I was thinking more of people who wander to a thread from Latest. It happens in the Guns forum. Someone clicks on a thread, makes a comment that they think is like pretty reasonable from a DU point of view, gets swarmed, looks up at the top of the monitor, and says "OMG I'm in the Guns forum, where's the exit?!"
It would be the other way around here -- somebody dropping in and posting comments inappropriate to the group. But I'm personally willing to give them a chance to realize where they are, so I've posted "please read the post pinned at the top of this forum" in reply a couple of times -- with no further bad vibes emanating from those sources, so I do suspect they wandered in inadvertently.
There was one yesterday that a host was all for banning, and I wouldn't disagree, but barring further problems, I prefer to err on the non-action side myself.
Don't hesitate to contact a host if you have a specific request, though. I would also not reject a banning request where a group member did feel demeaned or attacked in violation of the SoP, myself.