He doesn't help himself at all with stuff like this, shouldn't be done on a public forum really.
However, it doesn't help the situation when somebody is repeatedly slagging him off all over facebook on various rugby pages and people start 'tagging' Derek in this stuff to make sure that he sees it and has to read it.
He rightly took a step back from twitter when he reacted badly to repeated provocation, maybe it is time for him to do the same on facebook.
The other bloke was provoking him repeatedly with accusations, Derek replies and gets jumped on. Is it fair? No, but Derek is in the public eye and needs to either learn to ignore it, respond more professionally or just walk away from facebook. Which would be a shame as his interactions with fans are generally great and in good humour but, like it or not, he is the public face of Leigh Centurions and needs to act professional.