It's the most recent and thus the most salient one for a lot of people in software. There are many other examples of neutral terminology that's become politically charged: "all lives matter", "color-blind", the OK hand gesture...
I completely agree that none of these rules are individually taxing and that the consequences of breaking them are unlikely to be severe. But when taking everything in aggregate - the sum of all the rules I know about, the concern that there could be new rules I don't know about, the tiny but not unprecedented chance that I could face severe fallout - the net effect is stifling. Again, not the most important problem in the world or even the most important problem I personally face, but still a problem.
"All lives matter" is a natural English sentence expressing the idea that every person's life matters. This is not a particularly controversial idea.
I recognize that it's also a non-neutral political slogan, and that modern speech conventions require people to avoid saying things that sound like controversial political slogans. But that's precisely the problem! I have to keep up to date with all major partisan controversies, a task I generally find quite miserable and pointless, in order to know which new phrases I should avoid!
I completely agree that none of these rules are individually taxing and that the consequences of breaking them are unlikely to be severe. But when taking everything in aggregate - the sum of all the rules I know about, the concern that there could be new rules I don't know about, the tiny but not unprecedented chance that I could face severe fallout - the net effect is stifling. Again, not the most important problem in the world or even the most important problem I personally face, but still a problem.