Perhaps one solution would be to take the 'live' element out of things. If anyone ever used to watch Big Brother (it was interesting in the early days), when they broadcast 'live' it would be a few minutes behind time, which gave Channel 4 the chance to censor the audio if someone said something offensive.
Maybe footballers should be allowed to use social media, but be tied into some kind of vetting service, so it doesnt rely on the judgement of the player in question.
You know, like when Rooney has to make an eloquent public statement which has clearly been written for him.
Clubs obviously couldnt run this, but the clubs could obligate their players to be signed up to a start-up service. One for Dragons Den perhaps!
Comapny could be called '*Kn*b Filter' or 'Pratwatch' or something...