Your friend makes some good points and you should give what he had to say some thought. Speaking anecdotally, I grew up in a town that was 95% white, very affluent, but moved later in life and graduated from a high school which was minority white. I think what a lot of people on this thread might have missed is that people who grow up in insulated, white communities often have idealized views of what people of color are like - fearing that they will be perceived as racist, they overcompensate and develop a mental image of racial minorities which is just unrealistic. When they encounter people from different backgrounds for the first time, this mental image is shattered as they realize that people of color are either 1. like everyone else, some of them are good some not so good or 2. if they go to a rough, urban school where a lot of their peers couldn’t care less about learning, the culture shock could lead them to develop racist views and generalize this experience to people of color at large. When I was finishing up high school, #2 was certainly my experience. Today I am no longer a racist but I have transitioned from a liberal on race to someone who is very conservative on the subject in that I oppose all affirmative action policies.
The idea that exposure to people of different backgrounds leads to greater understanding and appreciation is known as contact theory and it is widely panned by individuals and scholars across the political spectrum. It is a fanciful notion and misunderstands how people from insulated communities develop their views on race.