You tacitly identified why few whites don't have visible black friends. Once you are white and have close black friends, then you are shunned by other whites who don't understand why you're a "traitor." More white Americans would stand up proudly for racial justice if they weren't so afraid of being expelled from the tribe. Close family members and friends will drop you out of discomfort, fear, and plain racism. At some point, a desire for a fuller, fairer life has to overcome white fear.