The principle (being courteous), can not really be used to justify him staying Cleveland. That's a huge life decision, and no one would argue that he should be swayed one way simply because many feel it's the right thing to do.
Couple points on how it might effect his show.
1. As of late Wednesday night, everyone pretty much knew he was going to Miami anyway. There was little suspense left.
2. He only let Miami know just before the beginning of his show, and he could have done the same for Cleveland, which would have eliminated the possibility of them spoiling his show (more than it already was).
From what I understand about negotiations of this type, what Cliff Lee did is common courteous, but I can't say that with any certainty. Regardless, if you acknowledge that it would be the courteous thing to do, but you find that courteous to be unnecessary, then we've reached an impasse and it would be useless to take this part of the discussion any further. We'll have to agree to disagree, rather than rehash the same points over and over again.
On contraction, again, this just comes down to courtesy. It's not the most important thing in the world, by any means, but I don't think an NBA player should be openly pushing for other NBA players to lose their jobs. I agree with the general premise of his point, but I just don't think he's the appropriate messenger.