Even if you looked at it entirely from the point of view of your club, I think you still conclude that it's better to take £100m now than retain a demotivated player for 6 more months.Of course it is, you do what's best for the club. We can let Vinnie, Silva, Zab etc go for free because it's not going to affect us that much, regardless of what they've done for us.
Messi is completely different, it's not comparable to any player in the world apart from fake Ronaldo
If a City player had given his entire career for my club, I would at the very end feel dishonoured if I did not respect the player. It's easy to say that from our position I know.