They ARE professionals, by any sense of the word you care to use. They are being PAID to play this sport and the Oxford English Dictionary has that definition clearly down in black and white.
These aren't the starving BYU student-athletes of yore. Some of these guys on the court are making more than a large majority of the people watching them in the stands. They SHOULD be expected to perform as professionals because that is what they are. If they don't perform, they deserve the brickbats that come with bad performance.