There is a tendency when discussing hot button topics such as religion to resort to ad hominem arguments. These are arguments that attack the person making the opposing argument, rather than attacking the actual argument. Usually this is an indication that the conversation is over. One person has concluded that there is no point in continuing the conversation and attacks the other because of frustration over that person’s perceived “obtuseness” or other, even less complimentary, characteristics.
This sort of personal attack is a logical fallacy. An argument either stands or falls on its own merits. The motivations and character of the person making the argument may explain why that particular person is making that argument, but they do not invalidate the argument itself. Assuming that they do is not a logical conclusion.
Furthermore, the ad hominem argument cuts both ways to the same extent. For every personal vice or failing that those on one side might have, there is a similar vice or failing (usually the one diametrically opposite) those on the other side might have. For instance, the religious often accuse non-believers of simply being in rebellion against authority—anal expulsive in Freudian terminology. Similarly, the non-religious see the religious as being slavishly devoted to obeying authority figures—anal retentive in Freudian terminology. I think the non-religious are more correct on this point and a recent study bears this out. (Though some non-believers clearly fit the anal expulsive category.) It is more important to realize that when it comes to the primary issue it doesn’t matter who is wrong or right on this point. No matter what emotional motivation drives a person, the argument he or she is making is either valid and sound or it is not.
Whenever you hear a believer slide into personal attacks on you or on non-believers in general, you should pull them up short by pointing out that they are admitting that they don't have any good arguments on the main issue:
"Usually, when a person starts making personal attacks, that means he knows he has lost the argument."
"If you have any good arguments to make on the issue at hand, then make them."
Make it clear that they are not addressing the point and that this implies that they know they can't address it adequately.
Sometimes, the ad hominem argument is a bit subtle. A classic public example of this is Dinesh D'Souza repeated assertions that Kant explains why atheists are wrong, never explaining what exactly it was that Kant said that was so forceful, and implying that if you don't know because you haven't read Kant, then you are just "uneducated".
This is, of course, ridiculous. He was clearly hiding behind an authority figure and insulting anyone who disagreed. When you get this, simply point out that the person is not actually making the argument that he claims is so compelling, which implies that he knows it is not compelling.
The truth is that virtually no one actually reads Kant at any length anymore except philosophy majors or graduate students. The vast majority of people in modern society can be highly educated without ever reading Kant, he is just one of a number of philosophers in history who contributed a few ideas but whose actual works consist of thick tomes full of dense prose. Actually reading his works would be waste of time for anyone who is not studying for a degree in the subject. Most of us get enough exposure to his ideas just from reading more modern authors whose works include his ideas.
D'Souza's point was that Kant had explained why pure reason wasn't perfect--apparently enough people pointed out his cowardly tactics for him to finally come out of hiding and try to make the argument he said was so compelling. Arguing that pure reason isn't perfect is not an argument for rejecting reason altogether, and when a person embraces religion, that person is rejecting reason.