Understanding the branch renaming

Personally it hardly matters to me what the default branch is named; the name is only there so that the first branch doesn't need to be created explicitly, which is useful because a repository can do useful things with just one branch, but cannot really with zero branches.

But making a change like this still concerns me for more meta-level reasons. It seems clear that it's a *response* to trends in how people are using Git, rather than something that the developers independently decided would improve the software. It's been about five years since GitHub's initial experiment, and presumably they were not the first to come up with the idea.

And it equally seems clear that the choice to rename the branch from "master" to "main" has been a social signal. All the historical evidence I can find of projects and companies documenting the change presents it as a moral imperative — insisting that it's what everyone should do in order to create a more "inclusive atmosphere", or "community", etc. To my mind, the argument has all the markings of a classic "holy war" (albeit a fairly one-sided one). But on a purely technical level, the change is so trivial that I can only assume that advocates are actually sincere in their belief that a social problem is solved this way.

The problem I have here is that these arguments never actually lay out any *reasoning* that I can comprehend. Those who object are at most hand-waved away by pointing at the history of slavery in the USA (or perhaps mocked or derided for supposedly not knowing about this, or supposedly ignoring it). But putting aside the Americentrism, and putting aside that the word "master" has many other uses (and in particular, there's no meaningful sense in which the *other* branches of a Git repository could be called "slaves"), there's no explanation offered whatsoever of why a *mere reference* to atrocities of the past should be problematic (much less for one specific group of people, descended from the victims of one particular implementation of that atrocity).

After all, when the topic is discussed, nobody sees fit to *censor* the word "master", or "slave" for that matter. (Unlike some other words relevant to the discussion of American racial politics, which are so charged that nobody even cares about use-mention distinction in practice.) So if that's the standard for discussions that are nominally about making people from racial minorities feel comfortable — discussions that nominally are supposed to center the views of those racial minorities — then I can only logically conclude that simply seeing the word "master" in the output of a Git command is not actually traumatic to anyone.

So can someone please explain to me: what, concretely, is the supposed reasoning by which it would cause anyone harm, or inhibit "diversity" goals, to leave the existing default intact — or for that matter, for GitHub and all those other projects to have skipped making such a change?