Manchester United manager Sir Alex Ferguson has condemned Blackburn fans for their treatment of boss Steve Kean.
Supporters barracked Kean non-stop during Tuesday's 2-1 defeat by Bolton.
"I have never seen anything as bad," said Ferguson. "It doesn't say a lot for society. For goodness sake, give the lad a break."
Tottenham's Harry Redknapp, Everton's David Moyes and Newcastle's Alan Pardew are other top-flight managers to slam the behaviour of the Blackburn fans.
They all believe Kean is being harshly treated.
Ferguson added: "I feel for the lad. I tried to phone him but he probably quite rightly had his phone switched off."
Moyes walked out of Tuesday's match in protest at the way the Rovers supporters had behaved.
"I was disgusted with how football supporters treated Steve and the only way I could show it was by leaving at half-time," he said.
"If they had supported their team as well as they shouted at their manager, then I think the team might have got a result in the game."
Pardew, who worked with Kean at Reading, agreed that the Rovers fans were damaging their side's chances.
"If they want to carry on like they are doing, all they are going to do is harm their own team," he said. "I can't see the logic in that."
The League Managers' Association said the reaction of fans was "unacceptable".
Kean has struggled to win over the Blackburn faithful since he succeeded Sam Allarydce a year ago.
An LMA statement read: "The aggression and abuse over recent weeks has stepped well beyond the mark.
"It is to Steve's significant credit that he has shouldered this continued onslaught with dignity and professionalism and has continued to work with his players to try to improve results on the pitch."
Redknapp described the supporters' behaviour as "horrific".
He said: "I have never seen it like that. I just felt sorry for him. It was sad to see."
However, ex-Rovers striker Kevin Gallacher told BBC Sport that Kean's position had become "untenable", while former Home Secretary Jack Straw has added his voice to those calling for Kean to be sacked.
Straw, MP for Blackburn since 1979, told BBC Radio 5 live: "All of us have been extremely patient with the owners and with Steve Kean.
"But having been at the game on Saturday, and after listening to the one last night [Tuesday], I think that there is no option as far as the owners are concerned but to ask Steve Kean to leave."
Blackburn fans are also unhappy at what they claim is a lack of leadership from Venky's, the club's owners, from India.
The LMA said: "As new owners, the Venky's should build relationships, develop trust with their fans and communicate their vision on a regular basis in an open and visible way."