Are those terrorists genetically defective, under the influence of a virus, or what?

I have an odd pair of theories about why some terrorists strap themselves with explosives, walk into a crowd and blow themselves (and a bunch of others) up.

My theory is that they are under one or both of two influences. First, they are infected with a mental virus, some sort of self replicating hatred in their mind they cannot get rid of. The second theory (I realize is a bit radical) is that they have been exposed to violence and hatred for so many generations, that irrational violence has damaged their genetic make-up and made them even more prone to irrational violence.

I am not aiming this question at any religious group or nationality, but I am serious about my question.

Do you think this is possible? What is your theory?