Yeah as a history buff I spotted that when the episode aired and I was 14. Sometimes you just need to tell an actor no. For one thing Sisko had played Baseball with stars who came from racist times and never had a problem,so it was out of character him to let it bother him,and on top of that the problem that he was complaining about(Blacks not being allowed to stay in the hotels or gamble in the casinos)wasn't even a problem at that point in time. So it was a dumb preachy scene that came out of nowhere and had nothing to do with the over all plot of a comedy episode. It just felt strange and out of place.