If a player wants to go, belligerence isn't the best way to handle the situation. I don't think anyone here on OER wants to see him leave, I know I don't, but I also would hate to stand in the way of someones best interests.
If he publicly states he wants to leave (which I doubt he will) then we should trade him. If we get in Bennell, Yarran and Treloar for Lennon and some picks I'd say that's a decent effort.
Remember, if a good trade gets done, neither party feel they got the better of it!