“I disagree with what you say, but I’ll fight to the death to defend your right to say it”

any time someone says this garbage I ask 2 very simple questions (and I admit this is kinda "debatebro" energy so your mileage may vary)

1: Will you "defend to death" my right to attack free speech as an idea? (They usually say no)

2: Will you "defend to death" my right to dehumanize vulnerable groups and suggest collective violence against them? (They usually say yes)

This reveals immediately what they're about and even though arguing with them isn't worth it, if there's an audience of people, I think it lays the stakes on the table pretty clearly.