If we are going to take away a convicted criminals livliehood upon release, then it defeats the object of re-integrating them into to society, as gainful employment is a vital part of their rehabilitation.
The man is being released as in the eyes of the law he has paid his dues, and we want that man to play a positive part in society going forward. This means working, paying taxes etc. If we take this opportunity away, then we may as well not even bother trying to rehabilitate criminals.
People seem more intent on creating a vengeful society whereby the punishment is the most important aspect of a crime. It's not, first and foremost it's repairing the damage done to the victim (Crawliano's idea of a continued recompense from future employment is a good one). Secondly it's to rehabilitate the offenders, to help them become part of an improving society, working is key to this. Just because an offender's trade is in a well paid job, it doesn't mean we should discriminate the rehabilitive support and treatment they get, because the end product desired is the same.
However, that said, I would encourage the Football League taking a stance, whereby they'll accept ex-offenders back into the fold in efforts to provide gainful employment in their specialist area of trade; but to gain that acceptance they need to actively support groups that help the victims of their particular crime for the duration of their career's, a kind of Football community service. Tony Adam's running/supporting a sobriety programme, McCormick/Hughes drink /drive programme's, Evans, supporting victims of rape (although from afar), Otto, crimes of robbery/duress. Making these figures regularly face up to the victims or consequences of their crimes would be a continued contrustive punishment to level out the priveleged jobs they have, would mean they continue to give back to society, and get to continue gainful employment to rehabilitate them back into society.