Chelsea's John Mikel Obi has been given a three-match ban and fined £60,000 by the Football Association for threatening referee Mark Clattenburg.
Mikel admitted an FA charge following an incident in the match officials' changing room after Chelsea's defeat by Manchester United on 28 October.
The FA accepted the player had believed the referee had racially abused him.
However, the union Prospect, which represents referees, said it was "dismayed" at the "lenient" punishment.
In a personal hearing on Thursday the FA's Independent Regulatory Commission accepted the Nigerian midfielder's explanation.
"But for that factor the suspension would have been significantly longer," the FA said in a statement.
Prospect national secretary Alan Leighton claimed "far too much weight" had been given to Mikel's mitigating circumstances.
A Prospect statement added: "It is vital that officials were given real respect and this decision regrettably gave entirely the wrong message. A player in parks football found guilty of behaviour like Mikel's would have faced a long-term ban."
The FA investigated the allegation against Clattenburg which prompted Mikel's behaviour and found that there was no case for him to answer.
The police also dropped their own inquiry into the allegations that Clattenburg had racially abused Mikel, 25.
Mikel's team-mate Ramires had made the allegation and Chelsea later said they regretted the way the matter was handled.
Clattenburg missed four weekends of Premier League matches while the FA investigated Chelsea's complaint.