Does prenatal testosterone determine sexual orientation? A look at racial differences

The conventional wisdom is that sexual orientation, at least for men, is genetic, but the heritability estimates are actually rather weak.

Some researchers have theorized that homosexuality is caused by prenatal exposure to testosterone (T).  Baby boys develop into gay men if they are exposed to insufficient levels of T during a critical period of development, and baby girls develop into lesbians if they were exposed to high prenatal levels. The level of T isn't the only factor: individuals also differ in terms of how sensitive they are to T.

If such a theory were true, we should see racial differences in sexual orientation because blacks tend to be more sensitive to T than whites. Their androgen receptors genes located on the X chromosome tend to be more responsive to androgens. We should see a lower prevalence of black gay men and a higher percent of black lesbians.

The General Social Survey asks about sexual orientation.  Here are the responses by race (sample size = 26,227):

Percent homosexual
Blacks
Men  3.8 
Women  2.2

Whites 
Men  3.0 
Women  2.3

These numbers fail to support the theory for both men and women.  There should be more white gay men, but there are fewer.  There should be more black lesbians, but their prevalence is very similar to that of white women. 

How do black and white males differ in a way that would lead to more black gay men?  I'm not sure.  Greg Cochran theorizes that homosexuality is caused by some unidentified prenatal infection, and it might be the case that blacks live in conditions conducive to more infections.