I know your situation and I just make it clear it wasn't funny. It differs from group to group, most of them you can't just say "dude thats not funny" without being shutdown as a "triggered sjw" but if you can, do it. If you can't, just find a lot of ways to say this shit isn't funny without outright saying it, you can just not laugh and carry on doing whatever you were doing, as if it didn't matter at all. You can also try to make the call uncomfortable after they make their shit jokes if its a small group. Another thing you can do is mock the shit out of similar jokes and people who make them (depending on the group you might not be able to say its bad because it's racist but you might be able to say "damn this is reddit edge-lord tier cringe" or something when your friends aren't making the ones making those jokes, kind of showing that the jokes aren't funny.) You can also send similarly edgy memes dunking on fascists, slaveowners, landlords, and whoever else it should be directed to. You could also try getting them to "ironically" do communist stuff, make it out to be a joke and just go from there. Doing things ironically is the first step to doing things unironically, for better and for worse.

overall its a really fucking shit situation but I know how you feel. I don't know if there's any good ways to fix it this is just what I've done. I've thankfully gotten to the point where I can say "not cool man thats fucked up" and it matters but it takes a while to get there, especially if you don't always feel like you're part of the "core" of the friend group. I hope things work out for you man.