Ole Gunnar Solskjaer reiterated the need for Manchester United supporters to be listened to, but said protests had to be "civilised" after Sunday's anti-Glazer demonstration forced the clash against Liverpool to be called off.
Fan anger at the owners has been stirred up by the European Super League fiasco, with thousands of protestors descending on Old Trafford demanding change before the high-profile Premier League match against their rivals.
A number of fans broke into the stadium and invaded the pitch during the protest, while another group made their frustrations clear at the team hotel in the city centre.
"It was a difficult day for us," said Solskjaer, speaking for the first time since Sunday's postponement.
"Of course we wanted to play, we wanted to beat Liverpool for the fans because our job has to be getting good performances, good results on the pitch.
"That's the players' focus, that's my focus but, as I said before the game, we have to listen.
"We have to hear the fans' voice. It's everyone's right to protest, it has to be in a civilised manner, though. It has to be in a peaceful manner."
The Norwegian added: "Unfortunately, when you break in, when police officers get injured, scarred for life, that's too far. That's one step too far.
"When it gets out of hand like this, it's a police matter. It's not about showing your opinions anymore."