This isn't something that actually happens commonly and in fact one of the only examples of this I can think of is alt-right shitheels digging up Gunn's old tweets, which is covered in the video.Thanks for the summary of the video (can't watch it right now).
While I can see and agree to your point, it looks like it's more talking about boycotting than cancel culture though? Because for me, cancel culture is more about how people specifically look for dirt for no specific reason, or the need to react the fastest way possible to the tiniest bit of potential wrongdoing from someone.
Of course the exemples used at the are just needed consequence and responses from employers, but I feel like it's not really getting at what cancel culture is supposed to be. Or maybe I'm wrong and that's not what it is.
So by your own definition of Cancel Culture, Cancel Culture really isn't a thing.