They've been poaching every player who will even consider moving club for a higher salary. Tevez from Utd, Nasri and Clichy from Arsenal, Lescott from Everton, the list goes on.
If you sign such a bunch of mercenaries then you can hardly complain when one of them turns around and bites the hand that feeds them...
Oh come on now, are you trying to tell me they are the first team to do this. You could compile a list much longer of players that Utd, Liverpool, Chelsea and Arsenal have poached. They have just followed the blueprint