Every person has some bright line boundaries. Me getting married was one of my dad’s. He was ok with me being gay but struggled with that. Him not going to my wedding was a bright line for me. When he told me he wouldn’t go I told him to have a nice life. It took him a month to figure out I was serious. He then got to make the choice for himself. At the wedding reception, he and I were talking and he let me know how shocked he was that this wedding was just a normal wedding, although way more stylish and classy and less tacky than normal. To this day I have no idea what he thought happened when gays tie the knot, but as he’d been a baptist for 60 years at the point, I’m sure it wasn’t anywhere close to accurate.
I don’t begrudge parents who need time to process. The time and place they grew up, their religion, their friend groups, the news they consume all have a powerful effect on people. What I do not forgive are those people who let all of those built in prejudices keep them away from their children in the long run.