I understand your frustration. My former In-Laws had contempt for me because I wasn’t Catholic and didn’t speak Spanish. I was just the “big, dumb Gringo”.
Yes, they are like that. I have a friend and she is not accepted, tho she speaks Spanish, is not catholic. A pity, because she is a great cook and can is so arty and creates so many interesting things.
It’s a shame when an in-law is not accepted by the whole family. The snub nosers must think the family member is intellectually a dupe. Poor things.