Though actually that "White men can't jump" thing seems somewhat right if you compare Caucasians (Europeans, Semitics (Arabs, Jews), Persians, Indians, Russians) -- athletic abilities are, on average, of a slightly lower par than Negroids.
You are kidding, right? Don't you know all people are created equal, with exactly the same attributes. No group has any genetic attributes that benefit them over another.
Just kidding. Two things genetically different primarily responsible for "White Men Can't Jump" syndrome. Routing of muscles in "upper thigh" (over the butt - thus "Baby's got back" is an accurate observation) plus the ratio of fast twitch to slow twitch muscle.
Look at long distance running, where these attributes do not dominate the equation.
But these facts do not stand in the way of the racist NBA not employing more white men to better represent the general population.