Accusing the Prophet (peace and blessings of Allaah be upon him) of being mentally ill
Question

Recently, I read an article concerning Prophet Muhammed's validity. The article explained Prophet Muhammed was insane and suffering from a terribe psychological problem. Is this true? I think it is not, but a majority of people believe so. Is there any way YOU can defend Prophet Muhammed as being a true prophet?.
Praise be to Allah.Firstly: 
The Muslim must realize that there is a difference between defending Islam before Muslims, which is done by quoting from the Quran and Sunnah and other reliable sources, and defending Islam before non-Muslims who do not believe in the sources of sharee’ah, so we have to address them on the basis of reason and common sense. 
In order to answer this question we should realize that such things could not be said by a Muslim who believes in the sharee’ah of Islam, and that such words undoubtedly constitute kufr and heresy. Based on that, it is obvious that the people who said this are not Muslims and do not believe in sharee’ah, rather they are kaafirs who do not believe in Allah or in the religion of Islam. So we should debate with them on the basis of reason, therefore we say to them the following: 
This claim can only come from one who hates and is jealous of the religion of Islam, for jealousy and hatred only come to a person when he sees an obvious blessing, which gives rise to hatred and envy in his heart. When those who came up with this claim saw the Muslims and the obvious blessings that they enjoy such as peace of mind and tranquility of heart, and the rare occurrence among the Muslims of evils such as adultery and alcohol consumption, and the low numbers of Muslims afflicted by physical and mental diseases which are rampant among them (the non-Muslims), such as AIDS and other illnesses, and when they saw the glowing history of the Muslims and how they were masters of the world when they adhered to Islam, and other manifest blessings to which everyone attests, and they saw how many people were becoming Muslim every day throughout the world, that upset them and they feared the spread of Islam, but they could not resist it except by using the feeble trick of slander. 
Intelligent people agree that anyone who makes a claim has to produce evidence to confirm the truth of what he is saying, otherwise it is to be rejected and thrown back in his face. Where is the proof of their sinister claims? 
If an intelligent man is told that some person managed to convince many people, numbering in the billions, of a specific idea, and that they followed him in that, or that a man on his own was able to succeed in the elections – for example – or to convince the people to vote for him, this intelligent man would attest that this person was brilliant and intelligent and wise. So how about out Prophet Muhammad (peace and blessings of Allah be upon him) – may my father and mother be sacrificed for him – whom the Arabs and non-Arabs followed, whose message of Islam spread everywhere and whose message with which Allah sent him has remained strong until our own times, facts which are attested by everyone? Even those who make these sinister claims believe this deep in their hearts, but their envy and hatred have made them blind. 
Many of the enemies of Islam, such as the Orientalists who study Islam, affirm the virtues of Islam and the status of our Prophet Muhammad (peace and blessings of Allah be upon him), and they testify that he was wise and perfect. When enemies testify to the virtues of their opponent, this carries great weight. 
The Muslim should not pay any attention to these people with ulterior motives who lay in wait to attack Islam and its followers, and try to undermine Islam. Islam is not affected by the slurs of such people or by their praise either.
And Allah is the Guide to the Straight Path.