Or answer with "if you need validation of X then you're too stupid to be participating in this conversation about role-playing topic Y."
It's derisive AND on topic.
And that's important skill of a DM. A DM acts as a moderator in the old debate class sense, ensuring everyone has a turn and remains on topic. Players will of course occasionally go off on tangents, but when the tangent becomes the main time-user at the game table, the game suffers. Sometimes the DM needs to steer things gently, sometimes they need to be derisive.
The real, hard boundary can't be explicitly defined, and amounts to, "Pundit will know it when he sees it."
Another DMing skill is using common sense. "I know it when I see it" is a series of rulings at the game table. Invariably, players have no problem with arbitrary ruling which favour them, but often have problems with arbitrary rulings which go against them. And this is why the DM wears the Viking Hat, to slap down any whinging.
I'm sure that thoroughly dismissing or outright banning people for having the audacity to ask why anyone would oppose BLM will not be used by detractors as ammunition to claim that this is some sort of "alt-right" forum full hypocrites who don't really believe in free speech, or unwittingly lead to it becoming an echo chamber where everyone just agrees with each other. :rolleyes:
A good game group will be indifferent to the opinions of other gamers about their play. And arbitrary rulings by the DM prohibiting excessive off-topic talk at the game table do not ever lead to the game group becoming an echo chamber, they lead to the game group
focusing on the game. when you get together with friends at a bar for wings, beer, and cigars, who stands over your shoulder telling you that you can't talk about A or B? No one does that.
That's the difference between a group gathering for purely social reasons, and a group gathering for a
social creative hobby. Pure social gatherings do not require very strong boundaries. Social gatherings which are also for an rpg session, for a football game or whatever, do require some boundaries. Being at a D&D session and complaining that the DM expects you to play D&D is like being at a football game and complaining that the referee won't let you shoot hoops.
That's not what you're there for. Rabble rabble I agree rabble rabble.
Random interjections from players rarely help the flow of the game session. Wait for your turn in combat.