Wayne Rooney has slammed Millwall fans for their "disgraceful and mindless" booing of players taking the knee.
Millwall and Derby County players showed their support for the Black Lives Matter movement ahead of Saturday afternoon's Championship fixture.
Players taking the knee was met with boos from the 2,000 fans who were returning to The Den for the first time since the coronavirus outbreak.
In response, Millwall released a statement condemning the actions, which have left the club "dismayed and saddened".
And Interim Derby boss Rooney - who said he was "surprised" by the incident in his post-match interview - took to social media on Sunday to rebuke the fans responsible.
He wrote on Twitter: "Yesterday I witnessed the disgraceful and mindless behaviour by a large section of the Millwall supporters in the stadium.
"Prior to the match, we were aware of the possibility of a planned disruptive response during the taking of the knee in support of the BLM campaign, but nothing prepared us for what we heard.
"I was proud of my players and staff for not letting the fans deter them from continuing to present a positive and important message that taking the knee immediately before a game sends.
"The professionalism of the players on both sides throughout the game was a credit to our profession after such an incident.
"On behalf of Derby County, I want it to be clear to everyone associated with the club that we represent all sectors of our community, regardless of colour, gender or sexuality.
"Fans being allowed back into the stadiums is vital for the wellbeing of everybody involved in our sport, from fans to players to chairmen and owners.
"It is therefore really important that the vast majority of us show respect and support of each other and do not tolerate or accept the actions of the mindless few."
Derby picked up their second win of the season with a 1-0 victory in east London thanks to Jason Knight's second-half goal.
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