They're apologizing because Grub was offended and that is not the way \m/ wishes to communicate with foreign dignitaries, especially when they were not warned of the happenings in #\m/. the rest of the apology goes out to the general populace of CN, as a courtesy to them, stating that they should stay out of #\m/ if they are offended by racist jokes, etc. so they don't have to make this apology over and over again.