Well, the line of cancelling someone until they literally cannot attain food has not been crossed... yet. But if say the Nazis were selling organic food to fund their activities, plenty of people would say it's wrong to sell seeds to the Nazis.
I'm not saying that I support this, just that this is what I see the "duty to cancel" arguments implying under these circumstances.
On the original point - it seems to me that the whole cancel culture is just an attempt by a vocal minority to bypass democratic system. Centuries of lawmaking have made some things legal and others not, walking very thin lines between good and bad decisions in order to maintain the balance between totalitarism and lawlessness - and suddenly a mob of random internet dwellers think they can get their way by throwing tantrums and bend the rules as they wish.
I'm annoyed at the very efficiency with which mob manages to cancel whoever does anything remotely "unacceptable" by their unwritten, "come on dude we all know that", rules... It seems like the futute is likely to be lead by loud demagogues skilled at tapping into the mob rage of the society and cleverly weaponizing it against their political enemies. Like always.
If you went to high school in the US, you probably read “The Scarlet Letter”. That’s about someone getting canceled, too.
Shame for behaviors frowned upon by your community has been with us forever. Even chimps throw bad actors out of the group.
That whole argument seems like a badly disguised call for total surveillance.