I'm a college teacher. Many years ago, I had several black students insinuate I was racist for requiring them to be on time for activities and meetings. Their rationale: "You need to know that we operate on 'black people's time.'" In other words, being late was part of their "culture," and I was being insensitive for not allowing for that. When they didn't show up for a field trip on time, I left without them. It was amazing... they were on time for future field trips! You do not make excuses for bad behaviors or attitudes.