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

Firstly: 

The Muslim must realize that there is a difference between
defending Islam before Muslims, which is done by quoting from the Qur’aan
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 Allaah
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 Allaah 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 Allaah 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 Allaah 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 Allaah is the Guide to the Straight Path.