I have a D&D session with a very left-leaning Democrat as the DM (he even used to teach courses at a liberal arts college), and he has been "subtly" (read: "very goddamn blatantly and aggressively") making comments about "evil/dumb/stupid" Republicans during our sessions.

At this point, I'm ready to call him out on it in front of the whole group the next time he tries it, and if he keeps it up after I call him out, I'm just going to leave the session at that moment and not come back. I only even play D&D to give myself some escapism and some in-person laid-back social interaction. If it's just going to get political despite my consistent requests to keep the politics out, I'm just going to leave.