Ole Gunnar Solskjaer has declared that anybody who sends racist abuse to Manchester United players cannot call themselves fans of the club.
Anthony Martial and Axel Tuanzebe were targeted after United's 2-1 home defeat to Sheffield United on Wednesday, receiving vile messages on Twitter and Instagram.
What was striking was that many of those directing the abuse professed to be United supporters.
United manager Solskjaer on Friday echoed the club's call for social media giants to step up efforts to clean up their platforms.
But he also addressed those sending the messages.
"It's just incredible that we have these scenes still, or this abuse, still in 2021," said Solskjaer.
"We've been campaigning for a long time now in the Premier League and, to be honest, I think it's working, but there are still some people that haven't got it.
"They hide behind social media, are anonymous and it's unacceptable. It's disgusting.
"They're not Man United fans anyway when this happens. We're standing behind every single one of our players."
Solskjaer was asked about how Tuanzebe, who is just 23 years old, was handling the jolt of being sent overtly racist messages, and said the defender was "fine".
"Obviously it's not nice," Solskjaer added. "He's a strong boy, a strong character; he's got good support from his family.
"We're his family in the club, his team-mates are his family. It's something we don't expect to see now, but you're not really surprised when it happens once in a while because, as we said, there are some people you feel sorry for. That's what you have to do for these individuals."
Captain Harry Maguire said on Thursday that the club "will not tolerate" such behaviour, while United labelled the offenders as "anonymous mindless idiots", calling on social media operators and regulators to clamp down.
Solskjaer, whose team play Arsenal in the Premier League on Saturday, believes any avenues for sending abuse must be closed off if users are posting with a sense of impunity.
He said: "I think the social media platforms needs to be looked at. If you can create anonymous accounts, abuse people, of course it's not right.
"We'll work together with everyone to stop this nonsense."
