I've read up on these types.
The logic is that those who they kill would be banished to hell anyway, so it's their moral obligation/duty to kill these people to propogate their political/religious beliefs.
There are a lot of surveys done, but it's basically linked to Christian fanaticism. I say fanaticism because the logic they use to justify their rationale for just about everything is inherently flawed and based on a very strict method of text analysis (ie the Bible, the Constitution). Kind of like extremist Islamic fundamentalists and their analysis of the Koran.