There is a lot of hypocrisy within the airlines about this. The remedy is simple and doesn't require costly legal intervention. They should adopt the same approach as football grounds and pubs, etc. Work collectively and ban them from all outlets. It would be a genuine deterrent if offenders were banned from all airlines.
I seem to remember some long necked lout who calls herself a super-model, being banned from BA. She was promptly feted by Virgin and welcomed with open arms.
I have very little sympathy for an industry which, for profit, compounds the problem. You allow them to board drunk, ply them with drink and fail to act firmly. I was recently on a Paris to EMA flight, where a passenger was told three times to pipe down before we even left the gate. Everyone knew he would a nightmare the whole flight, and he was. Why wasn't he disembarked? Because it costs money and that is more important.