I'm in favor of property rights. Even for closet racists! Does that make me a Democrat? LOL!
But property rights are rights recognized by the government. That doesn’t preclude individuals from signing contracts under terms by which they may be forced to give up participating in a voluntary association such as the NBA.
There’s a difference between an association forcing a sale out of membership and an individual illegally having property stolen or seized. In this case, if the owners go through with forcing the sale, Sterling will at least be able to hold up the sale while it works its way through the courts, which will look to confirm whether the forced sale is within the other owners’ rights.