I think a good definition is probably helpful. Note that I use the phrase "actionable" in the sense of "actionable" facts; the action is some response to the event; an event is actionable if one should respond to it (in this case, stand against or condemn or ban the expression).
- The idea that offense is an actionable harm, or
- The perspective that there are significant other categories of actionable harm in expression (such as blasphemy or not being affirming or indirect marginalisation) that can be done without a reasonable belief that the speaker has sexism/racism/etc that is being expressed
This definition is at least partly incomplete because it doesn't fully capture the distinction between, say, criticising a piece of art for being bad art or an idea for being ill-formed (which are not relevant to the term) and not calling some foreign head of state "sir" in a play (which likely is relevant to the term); this is lightly implied by the term "activist", but it's hard to really capture it deeply, and that term "activist" is itself problematic because it ranges from actual activists to speech codes that might come about as a result of activism to lese majeste.
As any programmer or philosopher mourns, it's hard to be precise without being very wordy, and when one is wordy it's easy for an idea to be lost among its details. Maybe we need short-definitions and framework-definitions when we propose ideas. Or something.