Sometimes in the field of dawah, this is not just with non muslims, people start mocking Islam. How come this? And how come that? The advice given to us by Allah is to walk away at that point, that is the best course of action. The people at that time are not ready to listen and you will end up doing more damage than good. This was the advice given to Rasulullah (peace be upon him), so we should never let our egos get in the way.