The Argentinean wing-back was shown a straight red card by referee Mike Riley for a foul on Paul Scholes in what proved to be a key moment in our 4-0 Premiership defeat at Old Trafford.
Scholes was brought down as he attempted to latch onto van Nistelrooy's pass, but replays later suggested that any offence was committed outside the penalty area.
In fact, Mr Riley initially appeared to wave away United's appeals but he acted swiftly after his assistant flagged. Taricco was sent-off, van Nistelrooy slammed home the penalty and at 2-0, with ten men, it was all over.
"It was a diabolical decision," blasted Glenn. "We will appeal, without any showdow of a doubt, because it was an unjust decision.
"He was was one and a half yards outside the penalty area. It should have been a free-kick and a yellow card. If we can't get those decisions right, where do we go?
"It's a key decision, because at 1-0 down going into half-time I felt we were very much in the game. People might look in the paper in the morning and at 4-0, it looks like we got a drubbing, but in the first half we had lots of possession, chances before they scored and I would have taken 1-0 at half-time.
"We might have got something out of the game, but it was never going to happen after getting Tano sent-off and going down to ten men."
Glenn Hoddle has promised to appeal against Mauricio Taricco's sending off after what he described as a 'diabolical decsion' against Manchester United on Wednesday night.