Why are just about all conservatives old white men?

It's the phenomenon of the shrinking White Man's power. That's the fallacy, anyway. Old white men like what they have, mostly because they didn't need to work for a lot of it. They see anybody else reaching equal ground as somehow stepping higher and they can't have fairness all across the board. They would no longer be special. Or powerful. Or influential. So they vote for the candidates most likely to inhibit change, protect the status quo and pander to the mainstream middle class white American.