The main distinction between a christfag and a normal polite Christian person is that a christfag's religious discussion to his or her fellow christfag will make any non-christfag bystanders who just happen to be in earshot, want to claw their own brains out.
christfag 2: Well, it IS the christian way to help everyone and love equally
bystander: (thinks) oh my god, somebody fucking kill me right now
bystander 2: YOU WANNA KNOW? WHY DON'T YOU ASK HIM YOURSELF
*bystander 2 kills both christfags and they live happily ever after*