In a football crowd it can be a combined welcome. Some may want to cheer him, some may want to boo him. Whichever is the stronger will prevail I think. That is how it normally works.
I personally don't have anything against him. If someone offered me a massive pay rise to do the same job just down the road, I would also want to go there. So I think he is entitled to look for a bigger pay packet. The fact he signed a contract means it is not up to him to leave just yet, but he is entitled to ask to.
The fact the decision is to keep him is not his decision nor is it his fault someone wants him.
As to what response the crowd will give him. I think that is up to the gods and the 'Mob' mentality that prevails in a football crowd.