I mostly agree with you, but I think there's a fine line between what I'll call white privilege and white preference.

White privilege is a complex system of societal advantage. There's nothing Sam (in this case) did to deserve that privilege, but there's also no reason to condemn him for using it to live the best life he can.

White preference is a racist dynamic whereby a white person is preferred over a minority solely because of the color of their skin. There's no doubt this exists too, but it's a deeply disgusting offense that's hard to prove.

It seems to me that a number of people in this thread are conflating the two. You're right that we don't know what's going on behind the scenes at YC, but I think we can give them the benefit of the doubt that white preference is not at play here.