> For example, it’s probably legal to call somebody a transphobic slur in many parts of the world but to suggest that trans people shouldn’t attempt to avoid or “cancel” such people is ridiculous.

That's not what we're talking about here, are we? We're talking about a public dogpiling.

And, TBH, your example is a poor one; while it's not illegal to slur/slander someone, there are legal remedies that dont' involve a global request to followers of a specific ideology to pile on.

Avoid people you don't like? Certainly. Join a campaign to ostracise someone you never met and never knew existed until your ideologues extended an invitation to mob them does not leave you on the right side of history.