> a congregation member asking "you believe in god, right?"

That's a very good analogy.

For some, believing in god or not doesn't matter much and they'll go to church mostly to make friends and be part of a community.

For others, being expected (or not) to believe in God is a no go, and losing friends/family holding these expectations will be a price to pay.

We all have our boundaries, and disagreements on some specific topics will be out of them. Cutting friends/family with incompatible stances is just one instance of that IMHO, be it political, religious or anything else that matters enough.