Assuming you genuinely made a sincere effort and could not come up with plausible reasons for the resistance, I'll mention a couple that immediately came to my mind:

- Breaking existing conventions

- Using "being offended" as a way to control someone else's language

I can see resistance, but I'm surprised by how much.

I see the inconvenience of the former, but I don't see how it ignites the passion I see in these disagreements. :%s/master/main/g should go a long way, right?

The latter is nothing new; it's the Overton window, which has existed for a long time. This issue seems like a small shift in the window.

The Fuhrer analogy is a typical stretching of reality and truth to suit your argument. Master / slave in computer science has deep roots. Parallel ATA, master clock, databases, distributed systems. There have been multiple african american technologist who have come out saying it's not offensive, I am willing to bet the people that are pushing for the change are in fact not african american but white. Thus virtue signaling, without actually taking the group who is affected into account and polling their opinions.