I think this is where the specific definition of “nice” is crucial. I think it’s very possible to still be “nice” while also being confrontational or standing up for things, and in fact, doing it nicely but without backing down can sometimes be extremely effective.

I know the “nice” you are referring to, where someone uses it as a shield for uncaring, selfish behavior. I’d of course rather have someone who isn’t so “nice” who earnestly tries to do the right thing than that kind of nice.