Let me explain. The reason why generalizing people based on physical attributes is so damaging is because it creates unreal and artificial barriers between peoples. It creates a sense of superiority in one group (e.g. white people) and puts down another group, which also reacts by declaring itself superior (e.g. black supremacists). This is a recipe for disaster, and has worked numerous times in our conflict ridden history.
Interestingly, the differences in physical attributes may be insignificant or even artificial and non-existent (see Hutu vs Tutsi of Rwanda). The result is all the same. There are people who try to play up these differences, for their own personal gain. This was done successfully in Rwanda, Yugoslavia, and between Pakistan and Bangladesh, among many others. You and your "friend" continue in the same tradition.