They ended up producing a "manifesto of inclusive software" where they listed every word they considered offensive and what it should be replaced with and made a very public announcement regarding the change.
The only response to their email was my (black) colleague asking if the branch renaming could be postponed to after a release because he didn't know what it could break in the build and release automation in case "master" is hard-coded somewhere.
This apparently started a lengthy thread between him and the 5 PMs where they explained to him that the reason he wasn't supportive of the change was because of the "systemic and cultural racism" he apparently internalized.