Don't do that. They're Christians because they said so, there is no standard or membership card. To act like the bad ones aren't "real Christians" is a cop out and ignores the problems within your religion. Own it, fix it, re-educate your fellow believers, don't act like they're not real and sweep them under the rug.
You may have gotten the impression that I'm claiming their religion. I do not. I just figure they all specifically worship a guy who was definitely homeless and born in a barn.
The same right as every other Christian who has believed in and committed atrocities over the last 2000 years- they worship Christ.
You don't have to follow your religious leader's teachings to worship them.
Most of the Germans who participated in the Holocaust called themselves Christians. Some devoutly said their nightly prayers and went to church every Sunday.
Translation: Whatever "sin" one conducts has none of the consequences, which have been well described and in short, have nothing to do with real life, and one must be accepted by the community via the magic word invocation.
All the rest is just nonsense for anyone intelligent enough to ask questions.