Let's see... on their NBA Finals teams, they had Karl Malone, Bryon Russell, Shandon Anderson, Jacque Vaughn, Chris Morris, Quincy Lewis, John Amaechi, among others... and Jeff Malone and John Starks were the starting shooting guards before and after Hornacek. I don't buy it at all.
If there is any reason why the Utah Jazz have more white players than other NBA teams, it's because black free agents are far less likely to want to move to Utah. Salt Lake City isn't exactly a hub of hip-hop culture. I'm sure the Jazz management realize this, and thus go after European players whenever possible.
Now, if anyone wants to have a discussion as to why white players are always "well-schooled in the fundamentals" while black players are "natural athletes," we might be onto something.