if someone gives an opinion about you which isn't fact

Like I've told you before, choose your battles wisely.
Everybody has an opinion whether it's based on truth or not. Nothing you can do to change that.
Your opinion of ypurself is all that matters.

Sounds like the epitome of similar world.
Once upon a time time it would bother me, not now. It means nothing, it's just their own narrow minded bias. It doesn't change who you are. Let them think what they want, it's their problem.

Depends on how much you value their opinion. If you need their approval in your life ser them straight if not laugh it off and make them wonder.

Unless this person holds a 'position of power' over you (parent; boss;...bank Manager ?) Their opinion is only worth the value you give it.

Let them believe it, not worth my time explaining if they do believe it.