A bad idea
The ar emany problems with teh proposed change.
The terminology of using master for the default branch is well established, changing it now will cause confusion and this will be inefficient and a source of unnecessary future issues so the change does have costs associated with it.
The second problem is that the change in any case in no way addresses any real issue in a substantive way, in so far as racism exists it will not alleviate or reduce racism. What it does is give the appearance of doing something while actually doing nothing, a pure gseture, which if it has any effect at all is to undermine substantive change.
The third problem is that the master in this case clearly refers to the concept of a master copy and is a better name than main.
More broadly the concept of master and slave which is a very widely used and useful design concept is very sucintly and accurately conveyed by the terms 'master' and 'slave'. Using terminology based on an analogy to a ubiquitous facet of human history which is fortunately nowadays illegal and righlt reviled in no way suggest to anybody any approval for it nor do I believe it causes any pain, suffering or disadvantage to anyone. It does provide a hook to people who want to be offended to claim offense. If we continue down this road where wil it end. Killing a process would logically seem even more offensive than master and slave,
should we stop calling connectors male if they have protuding pins making contact and female if they have a recepticle to accept pins? Whatever other terms are chosen, they will be less clear, cause more confusion and those who want to be offended will still find something to offend.