I wonder about this: while I don't agree with the idea, it seems legally questionable. If, hypothetically, the KKK got such a jersey and pasted racist slogans on it, the NBA could reasonably claim the people doing so were unjustly associating its brand with causes it didn't support. They would be using the NBA brand in a manner in which they had not received license to use it. I think the same thing applies here: while I don't approve of this action by the NBA, they could have grounds for legal action against someone doing this (though I imagine it would make a bad PR situation even worse).