Obviously the league wants to keep the "help" in line, not limited to keeping rabble like Le'Veon Bell to a minimum. Other than through contracts and CBAs, you do that by calling in to question his character, manhood, toughness and anything else you can.
Case in point, a news snippet recently referred to his hold-out as a "stunt". Sorry but going over Niagara Falls in a barrel is a stunt. This is someone applying the minimal leverage they are afforded under the terms of their employment. I'm not a Bell fan but I did draft him and his vilification is unfortunate - not surprising but unfortunate.