It seems odd that many who prefer white skin to dark spend hours and money darkening theirs via tanning. Why?

Well the obvious explanation is that your assumption is completely false. They don't prefer whiteness. Most people consider paleness to be rather sickly looking and want to get some sun.

You're so brainwashed to see a racial element in everything that evidence to the contrary just doesn't compute with you.

See my answer to Zietgiest.

He's wrong as usual.