Fine them all two weeks wages that should give them the discipline they're craving!
But seriously...
Don't be scared to fine the **** out of players that get sent off, talk to the press, seriously underperform, punch people etc. The good ones (personality wise) will accept it and improve, the bad ones will kick up a stink and make it pretty obvious you should get rid of them. They will probably unsettle your team somehow in the long run anyway and it could be at a bad time. Sell your stars if they are acting like babies and buy some real men!