Head coach Mark Bonner was quick to condemn the small number of Cambridge fans who booed while players took the knee before their 2-1 victory against Colchester.
Players from both teams took the knee in support of the Black Lives Matter movement for the first time at the Abbey Stadium this season, but boos were clearly audible as fellow spectators quickly responded by applauding before the Sky Bet League Two contest got under way.
The incident followed previous examples at Millwall and Colchester this month.
The Lions insisted they were "dismayed and saddened" by events at The Den ahead of the visit of Derby on December 5, when the long-awaited return of supporters was overshadowed by booing when players took the knee.
Colchester's League Two game with Grimsby on the same day was preceded by fans booing the players' anti-racism gesture before kick-off. The Essex club's owner Robbie Cowling said afterwards that fans who want to boo players taking the knee are not welcome at the club.
Paul Mullin's brace set Bonner's side up for a deserved victory. It was made more uncomfortable by Michael Folivi's penalty but Cambridge claimed their first win in six league games.
"A small number of fans let our club down tonight," Bonner said. "What pleases me most is the small minority that booed were soon drowned out by loud applause by the majority that understand that this is about systemic racism and inequality. We're right to back that message.
"We've clearly got more work to do because that behaviour's unacceptable. We don't want the light shone on our club for those reasons. We're trying to be a club that stands out for all the wrong reasons. I want to condemn that behaviour.
"We made the game more of a challenge than it needed to be. We played well tonight, it was a good game. We had an attacking threat about us, we ran hard, set the intensity by our front two who worked their socks off.
"We gave away a ridiculous goal, we need to manage the game when we've just gone 2-0 up. It could have been more a more comfortable finish for us."
Steve Ball was left frustrated by the self-inflicted nature of his Colchester side's defeat.
"It was two really, really poor goals to give away," Ball rued afterwards.
On the first goal, he said: "We gave it away on the edge of the box, we didn't track the right-back and then it's a stupid foul to give away, then the marking's woeful. That's four parts which aren't good enough.
"Cambridge have a long ball in them, are very direct and into channels. Other than that I didn't see a threat at all. I thought they would only score off a mistake or a set-piece, which they did.
He reviewed the second goal, by saying: "Again we gave it away on the halfway line, a cheap possession turnover and they're onto us. They're a team that thrive off that.
"We needed more quality in the second half. The goal changed everything, we had to try and get on the front foot. We did get back in the game, had a couple of late opportunities but never managed to score.
"It was poor decisions on the ball, a poor free-kick to give away and obviously poor marking (for the first goal). That obviously sets a team like Cambridge off.
"In parts in the first half, I thought were the better team."
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