WhiteLiberals are fundamentally in love with the idea of their special moral goodness.
What makes their moral goodness special is two-fold.
First, it is self-sacrificially un-selfish. That is, Liberals are in favor of things that will benefit people they do not know, and who often loathe them. Liberals willingly give up their own benefits for the sake of these hostile strangers. (But if you push harder, you'll find that many WhiteLiberals believe that their race's 'crimes' deserve whatever losses they suffer...)
A Christian martyr could hardly do better. And in fact is less morally good than a Liberal, since the saint hopes for a divine reward while the Liberal merely feels it his/her duty to Do The Right Thing, without counting reward or loss. Liberalism is in many ways a secularized and toxic morphing of Christianity.
Second, its specialness is highlighed by opposition to the vile bigotry, H8, greed, superstition and stupidity of the Liberals' loathesome Other, The Conservative RightWinger. As John Derbyshire points out, the great moral Civil War of the last half century has really been between two groups of White people who loathe the sight of each other. If it's true that all politics is ultimately local, then intrinsic to the WhiteLiberals' moral universe is the stark opposition between them and their nemesis, the WhiteConservative.
Only Whites can really be Liberals in this sense, because when Peeps de Couleur take on Liberal positions, they are direct beneficiaries, as ethnics. There is no unselfishness involved. And they have no real Evil Twins to differentiate themselves from. Except maybe Condoleeza Rice.
Only Whites can really be Liberals because they are The Most Foolish People On The Planet. (c)