"Racial equality is worth fighting for, but how can anyone seek to do so by using submitting?"
What is "using submitting?"
I think it should be like this:
"Racial equality is worth fighting for, but how can anyone seek to do so by being submissive?"
Yes, it is okay to use rhetorical questions. In fact, that was the teaching method Socrates used to teach Plato.
However, as a matter of style some people do not like the use of questions in essays. I used to not like them, but now I do. Why did I change my mind? It was the result of something I noticed -- the effect an interesting question has on the reader's mind.
:-)