Using DF there is a higher probability that you will be grouped with players from other worlds rather than your own and it just so happened that the times you experienced rudeness was when running with players from other worlds.

If there's 1000 rude players from lets say 10 different worlds, you have a much higher chance of running into the 9000 rude players from the other worlds rather than the 1000 from your own.

As an alternative to blacklist in df you could switch to the battle log tab and make sure you disable party chat for it, although the easier method is to just ignore them.