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.
Some level of vetting has been a thing since forever. Companies don't want you on their payroll if you are a potential PR disaster waiting to happen, and this matters more and more the more digits are on your paycheck. If you are an open member of the KKK or repeating their talking points publicly, you're not going to get a job as the face of Lucasfilm's next Star Wars movie. Not in 2019, not in 1979. Social Media/Interwebz has made it easier to find out about that behaviour because people are dumb enough to make those statements on Twitter or recorded audio/video using their own names without a care in the world as if they were talking in some private event. What's so bad about exposing those?
You're talking as if people spend hours every day combing through everyone's Twitter feeds and whole Internet presence to see if they have done anything problematic, when it's just likely that maybe there's a recent repeat offense that gets people to remember that hey, this person that is about to star in the next hitfilm from Marvel has actually been a raging transphobe in the past too (but back then it didn't gain traction because people cared less). People often just remember some past instances of shitty behaviour instead of going deliberately in search of and then maybe do a 2 minute google search to find the clips they remember. Or maybe some random person is reading some past interviews and suddenly they just come up with something where an actor is being a racist shit and then they just share it like "wtf, was this a widely know thing?" on Twitter to their 5 followers and that might go viral. No one necessarily went looking for dirt but it just has a habit of (re)surfacing.
Besides, if anything, the contrary is closer to being true. It has actually usually been the alt-right shitgibbons who go around trying to DESPERATELY dig up dirt on progressive people who are trying to enact positive change in the world in mostly futile attempts of shutting up "SJWs" who have dared accuse their idols of any wrongdoing or spreading progressive, inclusive messages (see: the case of James Gunn or what is happening with the pedo-creep-sex-pest Vic Mignogna and his accusers where the alt right fans of Mignogna have tried to dig up dirt and flung shit at the accusers to undermine their sexual assault/harassment claims).
People like Kevin Hart didn't lose their Oscar hosting gig because of a poor joke, he lost it because he REFUSED to offer even the tiniest bit of an apology. Not even a half-assed "sorry if you were offended" non-apology apology. A straight out "I won't apologize." People have said and done similar or even worse things but the ones who offer (at least seemingly) sincere apologies and condemn their past behaviour without any caveats have been and will mostly continue getting away with stupid, hurtful & hateful shit (unless it's something on the level of "we should kill all the gays" and not just using the f-word).
