Well, death is not a bad thing (for me). But use death as a weapon , to hurt people... that's the unbelievably awful thing (for me).
There are some people who learn their whole life how to "serve their god" and one of the main lessons is that it doesn't matter what you want; at some point, you are gonna start to wonder what that god wants from you and the traning is so radical that you, actually, start to think that you can offer your life to keep serving this god... (in bad ways... again "bad" FOR ME ) and this is when the whole disaster comes ! even if it's not a god... your cause is stronger than your fear (supposing that you had fear of death once)
So these people are acting according to what they believe; they are more than willing to die since they think what comes after death is far better than their current lives and obviously they are not scared !