If you do something, or say something, and when I hear about it I feel less respect for you then I had done previously - is that cancel culture? Am I cancelling you?
If you're a musician or film maker or author who I appreciate, but it's then revealed that privately you have expressed racist views, and now I feel less respect for you and decide not to listen to your music or watch your films or read your books - am I cancelling you? Am I morally obligated to keep supporting you financially?
Fear over being "cancelled", in my opinion, is simply fear of a boycott. It's nothing new or scary.
[Edit: typo]
"I should have reflected on what it meant to not be on the same side of a movement largely led by young producers of color"
That's basically it in a nutshell: the quality of a movement, of an argument, of an opinion is to be judged solely by the minority or oppressed attributes we can find in its supporters.
It doesn't matter if PJ was against the unionizing for his own reasons whatever they might have been -- how they might have affected his benefits, financial reasons etc. His stance against the unionizing is viewed as a personal attack on the attributes of the supporters -- young people of colour.
Put another way -- is there any objection that PJ could have raised to the unionizing efforts that would not have resulted in this same outcome? I doubt it.
Edit: I read your comment again and I also am not quite sure what you're objecting to. If there was a movement by wheelchair-bound folks to convince a company to build wheelchair ramps, I certainly hope we would value their arguments over able-bodied folk, because the entire point is they're speaking out about what their experience as a minority person is, and what needs to be done for them to get equal access to a company space. Are you saying their attributes as a wheelchair-bound person wouldn't be important to making that argument?
But that example seems much more clear cut and simple compared to a unionization effort. I can think of reasons why people might not want to join a union (e.g., dues) but only very superficial ones for not wanting to build a wheelchair ramp.
To be fair, this is a muddled example because Eric Eddings complaints against PJ are more complicated than just "he didn't support the unionization", granted.
To me, most of "cancel culture" is just asking people in positions of power to be held accountable, which isn't a bad thing and also doesn't always require the person to be banished from society.