As I know from sad personal experience, shunning sinners is a critical element of evangelical Christianity. Children are taught in Sunday School, even at very young ages, that part of being a good Christian is not associating with unrepentant “sinners.” I can’t tell you how many times I heard that from the pulpit growing up.
I took it for granted, not realizing how it utterly contradicted the teachings of Jesus.
When I was 16 and already secretly an atheist, I made a big stir in youth group by suggesting that obese people should be shunned, given they had clearly committed themselves to a life of sinful gluttony from which they refused to repent.
Oh, the shock and horror. (Especially given how so much of Baptist life revolves around calorie-dense potlucks and dessert parties. Baptists can bake!)
It took the youth pastor about 20 minutes to realize I was attacking Baptist shunning teachings rather than obese people. When he realized what I was up to, he became furious and yelled at me to “Shut your frigging mouth!”
But he never was able to explain his obvious cognitive dissonance.
I was not his favorite person. ;-)