i don't think that this is correct. whites are 66% of the us population and blacks are 13%:
http://quickfacts.census.gov/qfd/states/00000.html
i cannot find data on the racial numbers of grade school and high school basketball and football players but i have a very hard time believing that, in the aggregate, more blacks than whites play these 2 sports pre-college because whites so far outnumber them and nearly every town -- white or black -- has both sports for youth.
i also have a problem with the notion that there are a lot of white guys who could be great basketball players but who happen to choose lax, hockey or tennis due to cultural reasons. pretty much every boy is exposed to basketball in the us because it is virtually free, is very high profile (in terms of tv or role models), is social and doesn't take a lot of pain to play (like say, football, where you get killed in most practices, or an endurance sport, which requires extremely painful workouts to improve). if you are a good athlete in high school and can play multiple sports well, basketball inevitably is the one that you gravitate to for these reasons. if you can play it really well, then you eventually get rid of the other sports to focus on it. i'm sure that there are exceptions (probably mostly in football) where guys ditch basketball for another sport, but the vast majority of the time it is the other sport(s) that get ditched for basketball.
the other thing to do is to look at the nba and see the dearth of white players. a couple of months ago at work we were bored and looked at who the best us-born white players are in the nba. it's not pretty. no all stars and very few players other than backups or role players. dunleavy may be the best of the lot.
i'm not taking either side of this discussion because i think that you can win with white or black players -- it's just that the white players that you can win with (eg, laettner or hurley) are much rarer and i think that some misinformation has been stated here.