If I'm going to spend my energy on something it seems like there's bigger things to tackle than pushing back against branch renames.
As someone not a U.S. citizen, the impact of PC is ridiculously huge. I know slavery and how bad it is. It appeared in my culture, and it is still there in some form too. However, the ENGLISH word "master" means not much to me. It is just a multi-purpose symbol, like many other words. As the meaning being a main branch, why bothering the renaming?
You claim that you are just spending your energy on something else, but in reality you are giving up the right to use your own language and to maintain the definition the meaning of a well-understood and frequently-used word.
That is why I just ignore or reject such PRs. I do not believe that enabling it is a good idea. It is not my job to improve their context-awareness either.