It's surprisingly more common than you might expect. I can't speak to others' experiences, but my parents taught me for two decades that I should always vote Republican no matter what, because "that was the true American way." I was literally mid-20s before I finally woke up to the conditioning one day and realized I disagreed with everything they taught me. It was a very hard year with a lot of self-reflecting, analyzing, etc, as I tried to unravel the conditioning and decide for myself what morals I truly believe in.

Now I rarely talk to them. I just can't handle conversations with them anymore, they are the antithesis to everything I believe in and stand for. They've said some truly vile things and, while I still love them and care about them, I had to accept that I'll never be able to change them.