But most people seem to have no such ethical dilemma. The dilemma only exists for those whose political views are already opposed to those of the project owners, and who refuse to contribute on that account - neither a neutral or apolitical position, but one of intransigent political opposition.

So rather than simply avoiding ethical dilemmas in favor of cooperation (because plenty of people are cooperating) what's being advocated here is concession to anti-BLM advocates exclusively as a prerequisite for their participation, and those are the only people condemning or demanding exclusion of anything (specifically, the political views of the project owners.)

Because again, no one is saying that people who don't support BLM aren't allowed to participate.

It's open source software, and as is often mentioned when someone objects to a project owner's right-wing views, software is apolitical, and contributing in and of itself is not advocacy. And forking is always an option.