I missed this one before. You need to look more closely at the data, you are making the classic error of assuming that because most sex offenders are white, whites commit sex offenses at a higher rate. What you are overlooking is that non-hispanic whites make up 63% of the American population (72% if you include white hispanics) and blacks make up only 13%. If you look at the proportions in the data you just cited you will see that whites commit sexual offenses at a lower rate than blacks do. The only reason they are mostly whites is that America is mostly white.
Specifically your data from your links says this:
% of total child molesters:
White 51%
African American 25%
Hispanic 15%
American Indian/Alaska Natives 2%
Asian/Pacific Islanders 1%
So 63% of white Americans commit 52% of the sexual assaults, while the 13% of black Americans commit 25% of them.
You've just been hoist with your own petard!