I don't think The Bible recommends we're to make judgements at all. That's the thing. "Remove the log in your own eye" "he who is without sin" "judge lest you be judged" etc. 

I'm not saying a serial killer represents evangelical Christians. Serial killers don't represent any of us. 

I just always pause when I see "who's a Christian and who's not" statements. I was raised with the understanding that Hitler could have been saved in his dying breath. No amount of "sin" determines an ability to judge someone's status with God.