No it would not be. Nobody is barring non-white people from Bitcoin. There is no oppression. There is no far-right neo-nazi agenda. It's just a matter of culture. African-Americans predominantly don't have an interest in open-source P2P currency projects. Society is not going to crumble into a Caucasian-driven tyranny because of this. Cultures may change, adapt, stagnate and so forth but nobody is going to be "oppressed" because of predominate interests among them.
Historically for much of the time voting was not restricted to whites or males, just to landowners. It just so happened that almost all the landowners were white males.
A Bitcoin economy would be the same: The people with power would be the early adopters (that's us! woo!), who are overwhelmingly white and male.