Slandering and Accusing Muslims
Question

Our Shaykh, I love you for the sake of Allah and I hope that you can tell me how to silence those who slander the scholars. There are people who accuse you of being extreme in labeling others as kaafirs (non-Muslims) and of Qutbiism (a group that claims to base its ideas on the writings of Sayyid Qutb) – as they call it. What is your answer? Please note that I am – as Allah knows – one of those who love you for the sake of Allah.
Praise be to Allah.May Allah love you, for Whose sake you love us, and may He bring us together in His mercy on the Day whereon neither wealth nor sons will avail, except him who brings to Allah a clean heart (al-Shu’ara’ 26:89). 
With regard to what you have said in your question, we advise you to keep away from everyone who speaks about your Muslim brothers or slanders them, or accuses them and casts aspersion on their intentions. The Prophet (peace and blessings of Allah be upon him) said: “O you who have spoken the words of faith but faith has not entered your hearts! Do not backbite about the Muslims or seek out their faults, for whoever seeks out their faults, Allah will seek out his faults even if he is in his house.” Narrated by Abu Dawood, no. 4880; classed as saheeh (authentic) by al-Albani. 
It is also necessary for you to advise these people to fear Allah and refrain from using such labels and names that divide the Muslims. With regard to offering advice and correcting mistakes, this should not be done by means of exposing people’s faults or casting aspersions on their intentions etc. 
With regard to the issue of takfeer (labeling people as kaafirs - non-Muslims), this is subject to further discussion. Describing as a kaafir one who has been described as such by Allah or by His Messenger (peace and blessings of Allah be upon him) is obligatory. Allah has described some groups as being kaafirs in His Book, as when He says (interpretation of the meaning): 
“Surely, disbelievers are those who said: ‘Allah is the third of the three (in a Trinity)’”
[al-Maa’idah 5:73] 
“Surely, in disbelief are they who say that Allah is the Messiah, son of Maryam (Mary)”
[al-Maa'idah 5:17]
But it is haraam (impermissible) to label as a kaafir someone whom Allah and His Messenger (peace and blessings of Allah be upon him) did not label as such. 
Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) said: Just as it is not permissible to label a specific person as a kaafir unless the conditions of labeling someone as such have been met in his case, so too we should not shy away from labeling as kaafirs those whom Allah and His Messenger (peace and blessings of Allah be upon him) have labeled as such. But we must differentiate between what is specific and what is general. 
Sharh Kitaab al-Tawheed, 2/281. 
See also question no. 21576. 
And Allah knows best. 
Moreover, everyone who levels an accusation against another person must provide proof: 
“Say (O Muhammad), Produce your proof if you are truthful”
[al-Baqarah 2:111] 
“Since they produce not witnesses, they are the liars in the sight of Allah”
[al-Noor 24:13]
This problem is widespread among some of those who claim to be religiously-guided, may Allah guide them, for they make accusations against people on grounds that are not regarded as something worthy of criticism in sharee’ah or that do not undermine a person’s religious commitment.  
Then they do not bring any proof of that, and they follow their own whims and desires, because it is human nature to appoint oneself as judge, praising and condemning on a whim.   
We must go against the whims and desires of our own selves and measure people by the criteria set out in Islam; we should make mention of their good points and advise them with regard to their mistakes. 
And Allah is the Source of strength.