Milsim communities are often more fractured than something like BF, just because the major milsim on the market, Arma, has so many different game modes with it's scenario editor. You have your big ones like King of the Hill, Wasteland, and [insert map here] Life, some that occasionally crop up that are popular like Exile. A lot of people just play with their groups of friends though, usually setting up a server with a PvAI mission, or sometimes PvP missions.
You do see a ton of people going around repeating the n-word in the popular modes like King of the Hill, Wasteland, and the Life modes, but the other gametypes it really depends on the community surrounding those. I'd say in the popular game modes, yeah the community is probably worse. I don't think you can paint milsim communities with a broad brush though since they're so fractured given the fact there's so many modes and missions and mods.
BF, especially modern BF, is not a milsim and I'd be surprised to see people playing it like one. It's not trying to be one and that's perfectly fine. The game is fun this way. There were mods like BF2's Project Reality that were more milsim-y, but that was also a mod.