Well, it isn’t. And you are assuming a very American perspective and projecting it on the world.
I’ve never lived in a once-slave-owning country, my forefathers never had the experience you are talking about (I live in Sweden). Yet (some) people of color in my country persist in the same tone you have — holding some form of grudge towards society as a whole when they should reasonably direct their anger towards the individuals they feel have wronged them. Preferably within this generation, as I think it makes sense to keep your grudges within reasonable limits if you want to be even a little bit constructive.
I resent this new type of identity politics where everyone is a member of some group first and an individual last. I resent being made a representative of my gender, race or social stratum. I have opinions, I act in society and I’m quite willing to defend both on the grounds that they are my opinions and my actions — not because I’m being defined as representing this or that.