The ruling on seeking knowledge with the intention of refuting the specious arguments that are made against Islam
Question

                I love to seek knowledge for many reasons, one of which is that I hope that it will be a means of drawing closer to Allah, may He be exalted. I also hope that it will rid me of whispers and doubts, by Allah’s leave, and I hope that I will be able to teach people what they do not know. This last point has caused me some confusion, because I heard a hadith which some scholars regard as da‘eef (weak), but they regard its meaning as sound. It is: “Whoever seeks knowledge in order to show off to scholars and argue with the foolish…” Now I want to specialize in knowledge of refuting the specious arguments that have been produced in modern times, because I feel that the specious arguments are becoming widespread, and it is Allah Whose help we seek. Will I be included among those who argue with the foolish if I go and argue with people on Twitter and the like, and if I seek knowledge for that purpose, is it regarded as arguing with the foolish?
Praise be to Allah.It was narrated from Ibn ‘Umar that the Prophet (blessings and peace of Allah be upon him) said: “Whoever seeks knowledge in order to argue with the foolish or to show off before the scholars or to attract people’s attention, will be in Hell.” Narrated by Ibn Maajah (253).
It was narrated from Jaabir ibn ‘Abdillah that the Prophet (blessings and peace of Allah be upon him) said: “Do not seek knowledge in order to show off in front of the scholars or to argue with the foolish, or to choose the best seat in a gathering because of it, for whoever does that, the Fire, the Fire (awaits him).” Narrated by Ibn Maajah (254).
It was narrated that Abu Hurayrah said: The Messenger of Allah (blessings and peace of Allah be upon him) said: “Whoever seeks knowledge in order to show off before the scholars or to argue with the foolish or to attract people’s attention, Allah will admit him to Hell.” Narrated by Ibn Maajah (260).
Even though there is some weakness in the isnaads of these hadiths, they support one another. Hence al-Albaani (may Allah have mercy on him) classed them as saheeh, when he said concerning the hadith of Jaabir:
Al-Haakim classed it as saheeh, and adh-Dhahabi agreed with him. It was also classed as saheeh by al-Haafiz al-‘Iraqi (1/52). It is as they say, if it is free of interruptions (in its isnaad), because Ibn Jurayj and his shaykh Abu’z-Zubayr were mudallis [i.e., they  engaged in tadlees, which is when a narrator narrates a hadith that he did not hear directly from his shaykh, without mentioning the name of the third party from whom he did hear it, using wording that may or may not give the impression that he heard it directly], and they were known for that. They also narrated it by saying ‘an (“from”, instead of saying that they heard it directly from a narrator). But the hadith is saheeh whatever the case, because there are corroborating reports concerning the same topic which strengthen it and are strengthened by it.
End quote from Saheeh at-Targheeb wa’t-Tarheeb (1/154).
Shaykh Muhammad ibn ‘Ali ibn Adam al-Ethiopi said:
This hadith of Jaabir ibn ‘Abdillah (may Allah be pleased with him) is one of the hadiths narrated in al-Musannaf, and it is saheeh. Al-Busayri said: The men of this isnaad are thiqaat (trustworthy), according to the conditions of Muslim. End quote.
And it is as he said, although its isnaad includes the ‘an‘anah [narrating by saying ‘an (“from”)] of Ibn Jurayj and Abu’z-Zubayr, who are mudallis. But the hadith is saheeh because there are corroborating reports.
End quote from Mashaariq al-Anwaar (4/485-486).
The apparent meaning of the hadith indicates that the person who learns about Islam for the purpose of arguing with the foolish is given warning of punishment, because he has not fulfilled the condition of sincerity when learning about Islam; rather his only aim is to learn how to argue.
It was narrated that Abu Hurayrah said: The Messenger of Allah (saw) said: “Whoever seeks knowledge that should be sought  for the sake of Allah, but he only seeks it for the sake of some worldly gain, will not smell the fragrance of Paradise on the Day of Resurrection.”Narrated by Abu Dawood (3664).
The sincere and sound intention when seeking knowledge should be to act upon it oneself, then to teach it to people and convey it to them, and to take Islamic teachings to those who are not aware of them, then to ward off the aggression of the transgressors and the misinterpretation of the evildoers.
Allah, may He be exalted, says (interpretation of the meaning):
“For there should separate from every division of them a group [remaining] to obtain understanding in the religion and warn their people when they return to them that they might be cautious”
[at-Tawbah 9:122]
“So do not obey the disbelievers, and strive against them with the Qur'an a great striving”
[al-Furqaan 25:52].
Shaykh ‘Abd ar-Rahmaan as-Sa’di (may Allah have mercy on him) said:
“a great striving” i.e., do not spare any effort to support the truth and suppress falsehood; even if you see them rejecting you and treating you rudely, still do your utmost and do not despair of them being guided; do not stop conveying the message to them just because it does not suit their whims and desires
End quote from Tafseer as-Sa‘di (p. 585).
So whoever learns with the intention of refuting the specious arguments of the disbelievers and advising the Muslims, this is a sound intention.
Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) was asked:
Do you have any advice for a beginner seeker of knowledge?
He replied:
Our advice to every person is to make his intention sincerely for the sake of Allah, may He be glorified and exalted, and not to let his aim when seeking knowledge be the pursuit of leadership, prominence or wealth. Rather his aim should be to alleviate ignorance from himself and from others, to adhere to the straight path, and to defend it and protect it. This is the best thing.
End quote from Liqaa’ al-Baab al-Maftooh (226/36).
If he needs to argue and debate whilst calling people to Allah, there is nothing wrong with that, because that is not the aim of his learning; rather it is a means of conveying the message. But he must argue in the way that is best, and within Islamic guidelines.
Allah, may He be exalted, says (interpretation of the meaning):
“Invite to the way of your Lord with wisdom and good instruction, and argue with them in a way that is best. Indeed, your Lord is most knowing of who has strayed from His way, and He is most knowing of who is [rightly] guided”
[an-Nahl 16:125].
Shaykh ‘Abd ar-Rahmaan as-Sa‘di (may Allah have mercy on him) said:
i.e., let your call to all people, Muslims and disbelievers, inviting them to the straight path of your Lord, which includes beneficial knowledge and righteous deeds, be  with wisdom , addressing each according to his situation and ability to understand, and the level of his acceptance and submission…
If the person to whom the call is addressed thinks that what he is following is truth or if he is a promoter of falsehood, then the caller to Islam should reason with him in the most courteous manner. These are the ways which are more likely to bring a response, according to both reason and the texts.
One way of doing that is to use evidence that he believes is sound, because this is more likely to achieve the goal and not lead to argument or trading of insults, which will defeat the purpose and is of no benefit. Rather the aim is to guide people to the truth, not to prove them wrong and the like.
End quote from Tafseer as-Sa‘di (p. 452).
Allah, may He be exalted, says (interpretation of the meaning):
“So do not argue about them except with an obvious argument and do not inquire about them among [the speculators] from anyone”
[al-Kahf 18:22].
Shaykh ‘Abd ar-Rahmaan as-Sa‘di (may Allah have mercy on him) said:
“So do not argue” that is, do not discuss or debate
“about them except with an obvious argument” that is, one that is based on knowledge and certainty, which should also serve a purpose.
End quote from Tafseer as-Sa‘di (p. 474).
Conclusion: learning Islamic knowledge with the intention of calling people to the religion of Allah, may He be exalted, and defending Islam, and refuting the arguments and foiling the plots of the disbelievers is a sound intention, provided that the seeker of knowledge does not focus exclusively on the branches of knowledge that are a communal obligation whilst neglecting those that cover individual obligations, such as the fundamentals of his faith and how to perform obligatory acts of worship such as prayer, fasting and so on.
It was narrated that Jundub ibn ‘Abdillah al-Azdi, the companion of the Prophet (blessings and peace of Allah be upon him) said: The Messenger of Allah (blessings and peace of Allah be upon him) said: “The likeness of the scholar who teaches people good and forgets himself is that of a lamp which gives light to the people but burns itself.”
Narrated by at-Tabaraani in al-Mu‘jam al-Kabeer (2/165-166); classed as hasan by al-Albaani in Saheeh at-Targheeb wa’t-Tarheeb (1/164).
And Allah knows best.