The union has made a wise decision to keep Clattenburg out of the spotlight while this investigation is going on, something that will benefit all parties involved.
The PGMO has decided to give the referee of Chelsea's match with Manchester United a weekend off following the allegations of his inappropriate behavior during and after the match. The union for referees had the following to say on the subject:
"Professional Game Match Officials believe that, with any football match, the focus should not be on the officials but on the players and the game itself."
"Mark Clattenburg is one of the elite referees in world football and, in these circumstances, the intense level of scrutiny would detract from the match and be unfair to the clubs and the supporters of both sides."
This seems like a no-brainer of a decision, but should not be looked at as any sort of indictment against Clattenburg for his in-game decisions on Sunday. Both the PGMO and FA surely wanted to avoid putting Clattenburg on the pitch immediately following these reports of inappropriate behavior, and it's definitely best for all parties involved to keep him out of the spotlight until this investigation has been concluded.
I'd imagine the PGMO and FA will not be pleased with either the performance of Clattenburg or his linesmen from Sunday, but I'd guess that matter will be dealt with separately. For now, it's good to see that they are keeping him out of the spotlight.