The anger that fans show towards a favourite player when they are sold is understandable, especially if they have forced the move (not saying that's the case with Maddison). People love these players - they pay hard earned money to see them, put their names on a shirt, sing their names and their actions on the pitch can define emotions for a whole week.
So when they leave it is akin to betrayal in a relationship, except that the relationship with fans and footballers is usually totally one sided. A transfer means no futher return on the emotional and financial investment made by the fan into that player while the player reaps greater individual reward somewhere else. The fan is powerless in the situation.
Staying angry/bitter, even years later, is a manifestation of the impossibility to reconcile those feelings of hurt at the transfer - the display of anger whenever that player is mentioned becomes a form of revenge in a situation that the fan had no influence over. A public display of hurt is as close to punishing that player as you can get under these unique circumstances. Letting the anger go equates to forgiving that player for leaving, which is hard to do in a one way relationship.
Imagine then that your friends are all congratulating your ex, in front of your face, on how well they've done for themselves since they left you. Salt in a wound.
