Ainsworth was annoyed at the 42nd minute dismissal of Joel Grant for a dangerous tackle on Andrew Wright, claiming the sending off was not the only decision D'Urso got wrong.
Wycombe found themselves two goals to the good inside 50 minutes as Dean Morgan scored twice.
But after pulling a goal back just before the hour through Richard Brodie, Redshaw struck late to salvage a point for Morecambe.
"I see things differently to referees," said Ainsworth. "There are a couple of things I saw differently to Andy D'Urso in the game but that's football."
Despite his irritation, Ainsworth singled out two-goal Morgan for special praise after the final whistle.
"Dean has been doing everything except score recently," he added. "He's a player with unbelievable ability. If you see him in training every day, sometimes you think 'why is Dean at this level?'
"He scored two great goals and he's causing defences all sorts of problems and that's why he's in the team.
"This is a new group that we've got now, we feel we wanted to win that game, but we had 10 men for 55 minutes, so I think a point is decent if I'm honest.
"If people come and see the game, they'll think '2-0 up, Wycombe are playing well' but it's always difficult with 10."