I fully realize that learning about fallacies, and how to have a proper debate with someone is not for everyone, but I do find it valuable even for those that don't engage in discussions to understand or recognize terrible arguments. One such argument, or more accurately said, fallacy, is an ad hoc swap commonly known as "No true Scotsman".
I don't remember the origins per say, but boy has it been helpful to me, specially because it seems these days that the enemies of nuance and reason, love using it to move the goal post, instead of admitting a mistake or a concession of sorts.
A terrible argument of this kind usually starts with a terrible and ineffective generalization of sorts. For example, someone could say: No libertarian would get behind the idea of Universal Basic Income, that's socialism! - then, I could retort - "You might do well to know that Milton Friedman believed in it's effectiveness and proposed it often".
In a "normal" world, the one arguing with me should concede that maybe, just maybe, the generalization was off. But, instead they double down on the assertion. "Friedman was not a true Libertarian then... he was left leaning.
As you can imagine, there's no point in continuing the conversation any further, the foundation for discussion can't be established and it is at this point that one could accept the futility of carrying on.
MenO