alt Hacker NewsNot really. Both mainstream political parties don't like each other, but by and large they don't attack someone for leaving the party (from what I've seen).
Perhaps if you are saying attacks of politicians switching parties, which I could see. But I don't think I've ever heard of republicans talking about exrepublicans or democrats talking about exdemocrats. I personally have switched from voting republican to voting democrat. It's not something my family really cares about and I still have good relations with them even though a number of them are pretty MAGA.
Cults will actually have lessons and classes about the evils of ex members. Someone brought up JWs and that's a pretty good example of what I'm thinking of.
I think you’re correct that mainstream leaders of the parties try not to talk about each other in that way and mostly succeed. But I absolutely do know family members and friends treat it with that level of zeal.