Assalamu Alaikum, According to hadiths, zakat is regarded as impure wealth and dirt of people. Hence the Prophet (pbuh) forbade for himself and his family. The anti-Islamists are making statement that if zakat is impure wealth and dirt of people, will not the poor people take it as an insult to them when they know that they are accepting something impure and dirt. How to answer them.

All perfect praise be to Allaah, the Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.

It is confirmed that the Prophet said: "Charity is not appropriate for Aal Muhammad (i.e. the family of Prophet Muhammad ) as it is the dirt of people." [Maalik and Muslim] The meaning of "the dirt of people" is that it cleans the dirt of the person who gives it, i.e. his sins and faults, as Allaah says (what means): {Take, [O Muhammad], from their wealth a charity by which you purify them and cause them increase...}[Quran 9:103] That is, it purifies them from sins and vice (immoral acts), and it makes them grow, i.e. it improves their moral character.

As regards saying that this is an insult to the poor, then the answer is as follows:

Firstly, if we presume that Zakah is the dirt of people and an insult to the poor, then repelling a dire necessity is given priority over looking at the issue of insult. For instance, in eating dead meat, there is humiliation for the person who eats it, because if it is said to a noble or mean person to eat from this dead meat, he will consider this as an insult to him; however, it is permissible to eat it in case of dire necessity, because if such a person is about to die, he would take the initiative to eat it greedily and he will forget about insult or humiliation, and it will not be said how this is permitted for them while it is a humiliation because every sane person knows that saving a person from death and harm is more important than taking into consideration the question of humiliation. The same thing applies to saving the poor from the harm he is afflicted with because poverty is greater than the question of taking into consideration the issue of humiliation and this is very clear. It is for this reason that Abul Waleed Al-Baaji said in his book Al-Muntaqa: “The poor are permitted to take it, in the same manner that it is permissible for them to eat forbidden food, in case of a greater necessity than this.” He also said, "A person who is poor is permitted to take it because of his necessity."

Secondly, the Prophet not taking charity is not just because it is the dirt of people, but this is just one  among other reasons which the scholars mentioned, which necessitated that and which is not existing in other people, among which is the following:

1 - If the family of the Prophet took charity, the Prophet's enemies would claim about it that the Prophet was calling people to give charity so that he would take it and give it to his family; Allaah says (what means): {Say, “I ask of you for it [i.e. this message] no payment.}[Quran 6:90]

2 - The hand that gives is the upper hand, and the hand that takes is the lower hand, and it is not befitting for the hand of the Prophet to be the lower hand.

3 - Charity is not permissible for the rich and Allaah has enriched the Prophet ; as Allaah says (what means): {And He found you poor and made [you] self-sufficient.}[Quran 93:8]

4 – Also, the society looks down on the person who takes Zakah and this is an actual reality although the Sharee’ah never ordered this. So, it is not befitting that the Prophet be in a position which makes people look down on him and believe him to be in an inferior position. If noble people are too dignified to take charity, then how come that a Messenger or a Prophet takes it.

Thirdly, the Sharee’ah did not oblige the poor to take charity (the so called "insult"), but it rather permitted them to take it, and there is a difference between forcing a person to accept an insult and giving him the choice to do so.

Allaah Knows best.