How could it not be used in such a way

As I said in point 3, many cultures overlap. White gays use of AAVE, for example, is not being used in a mocking way (I guess I should clarify - it very well can and sometimes is, I am simply speaking from a very general viewpoint)

they’re not congruous

Sure, but people that learn a language do speak it, both in the learning process and usually in practice.

using words from another language out of context can be considered racist

I already agreed with this point in my OP - there is very much a racist way white people can use AAVE. White people do not have some sort of complete immunity for using AAVE, that is not my argument

it’s a deeply complex and nuanced issue

I agree, which is why I think it is a ridiculous assertion to say white gays are stealing black women’s culture

In what world should a white person who does not typically speak AAVE...

Again, many cultures overlap. I don’t think there are many situations that would make it acceptable for white people to speak AAVE if they do not normally speak it. But I would argue that a significant portion of white people are involved with black culture in some capacity, considering the significant influence black culture has had on pop culture. Saying that a white person is racist because they use words they have been hearing since childhood is just poor logic imo