The faculty and students at my small minority-serving institution think of our environment as being supportive and cooperative. This is very important in CS, since programming is a team sport, and students are expected to seek help from each other (and TAs and me).
I have heard recently from two unconnected students about other students ignoring or being rude to them (such as walking away mid-question). The complainants don't give names, and I have no idea who they're talking about.
Almost all of the students in our program belong to at least one demographic underrepresented in CS and/or in the US. The students who have been mistreated belong to multiple such demographics and think that may be a factor. I have no way of knowing if they're right. Each is the only student of their cohort in their demographic.
What can I do to encourage students to better treat classmates? Some have been at the institution much longer than others. The ones who feel mistreated are newer arrivals. While my top goal would be changing students' behavior, we all know it isn't always possible to get people to change. If I can't get people to change, how can I know who should deserve bad citizenship grades or to not get letters of recommendation? I am not interested in furthering the careers of people who mistreat others.