Fernandes was given his marching orders in the 41st minute when he caught Tottenham midfielder James Maddison high with his boot.
However, the Red Devils skipper had slipped as he made his way into the challenge.
Fernandes' slip mattered little to Kavanagh, who immediately reached for the red card.
VAR opted not to intervene, forcing Fernandes to accept his fate and head back up the tunnel at Old Trafford.
Referee Chris Kavanagh brandished a red card for Bruno Fernandes in the first half
However, Young felt Fernandes was hard done by and should not have been sent off.
'I don't think it's serious foul play or its reckless,' Young told Sky Sports.
'I think the referee's got it wrong there.
Although he felt it was a 'petty' act, Jamie Redknapp agreed with Young's stance.
'Fernandes slips,' Redknapp said.
'It's petty. He sticks out his right leg. I think it's a yellow card.'
Darren Bent added: 'First time I saw it I thought that's naughty. I think it's more petulant than anything.
One user wrote on X: 'That's never a red card in a million years. Game has gone. He literally slips over and even then, the contact is minimal.'
Another posted: 'Never a red card Bruno slipped and never even got Maddison with his studs.'
A fan said: 'That wasn't a red card. Yes he slipped so wasn't in control but made contact with his heel on the shin. Not reckless.'
Another supporter added: 'I'm no Utd fan, but that is never a red card. Yes, he's slightly high, but he's caught him with his heel! No danger to the opponent whatsoever. Also, he slipped just before, which has to be taken into account.'
At the time of Fernandes' red card, Tottenham had taken a 1-0 lead thanks to Brennan Johnson as he tapped home a cross from Micky van de Ven.