| Last updated
A large group of United fans forced their way into the stadium ahead of the Premier League fixture with Liverpool, which was later postponed.
Footage showed a flare was launched towards the gantry, where Souness was on punditry duty for Sky Sports.
While Gary Neville, Roy Keane and Jamie Carragher defended the fans' right to protest, Souness condemned their actions.
Souness just said that someone threw a bottle of beer and it could have killed someone lmaoooo- ... (@neutralFC) May 2, 2021
"If that had hit any one of us, we'd be lying in hospital permanently scarred on one side of our face," he said. "So that ain't a laughable situation.
"Someone threw a full can of beer at us. Again, if that clips you in the wrong place, that might even kill you. So, let's not be tippy-tappy around the situation. That is unacceptable."
Souness also launched a surprising defence of the Glazer family, insisting United fans' anger at their owners is "misdirected".
"I don't think it will [have an impact]," he said. "The Glazers, since Fergie [Sir Alex Ferguson] retired, have given successive managers over a billion pound to spend. I think it's £719m net spend over the eight years.
"I think it's born out of United not being top dogs. These are serious, serious business people, I don't think this will impact on their thoughts. I really don't.
BREAKING: Angry Manchester United fans are staging a protest against the club's owners after getting inside their Old Trafford stadium.
Read more: https://t.co/UlMC47LNkj pic.twitter.com/dDtHI04cGa
- Sky News (@SkyNews) May 2, 2021
"We live in a country where you can demonstrate, you can vent your feelings, you're allowed to do it, but I still don't see it impacting on the Glazers one little bit. If you think you can bring serious pressure to serious business people who live 3,000 miles away, across the Atlantic, that it will drive them to accept a discounted offer for Manchester United, that will not happen.
"They've had to put collateral in, you don't just go to the bank and say I want to buy Manchester United, I'll need £500m or however much it costs to buy, without committing some sort of collateral.
"They've risked things to buy Manchester United, since then, they've given successive managers fortunes to spend. It's only since Fergie stopped that the success has stopped, and I think that irritates supporters and they have become the focus of their anger. I think it's slightly misdirected."
Chosen for YouChosen for You
Most Read StoriesMost Read