The question of 'what to be done' is a good one.
It's one thing to call out someone like the person shown in the link I cited above -- an easy call, you might say. (In fact, the blog cited does not indicate what happened to this person, whether he was asked to leave, etc.)
If I were Black, however, I doubt I would feel comfortable hanging out with people who seem to have no issue with -- for example -- displaying replica Confederate battle flags. (The point is not to debate that issue, but rather to make the point that many are sensitive about the subject, and have good historical reasons to be from the 1860s and the 1960s.) I think I might feel unwelcome, and not inclined to support the organization. At the same time, there are undoubtedly a good number of people honestly and enthusiastically supporting the right to keep and bear arms, who have a different opinion on that particular issue (and who are already established as members.)
So, asking this as sensitively as possible, what do we do in terms of outreach to get around problems like this?