Sure you can, it's called Affirmative Action.
In all seriousness, I doubt that the reason for attendance drop is the ethnic makeup of the players. You could make the same circumstantial case for an increase in non-American players. Correlation does not mean cause and effect. Hockey may not be a good example, as it is the yuppie sport of choice at the moment and will wane when the wine and cheesers find something new.
A high concentration of African-American players is not a new phenomenon to the NBA (or other professional basketball leagues). What has been changing is the quality and consistency of the product. College basketball and high school basketball remain entertaining because the length of the season means that all of the games have meaning, much like football, and the players are playing to survive to the next level every game. The length of the regular season in the NBA diminishes the impact of losses. I think that the number of teams and dilution of talent has also decreased the quality of the product.
The NBA, like all other pro sports leagues, are entertainment, just like the movies, concerts and other similar endeavors. This means that they all compete for the same expendable income. If basketball ceases to be entertaining, which it has, the dollars will move elsewhere. If the game opens up and becomes more entertaining, the attendance will pick back up, regardless of the ethnic makeup of the team.