Treviso secured their first ever victory over Ulster at Ravenhill, where McLaughlin's men had not previously lost in 2011.
It was also Ulster's third straight defeat as fly-half Kris Burton delivered an 18-point masterclass, and now McLaughlin's men will have to wait until October 29's visit to Parc y Scarlets for a chance to put the record straight.
"We're exceptionally disappointed," he said. "We were looking forward to getting back here and then to turn up and play like that in front of our home fans; we all agree that it wasn't acceptable from our point of view.
"We were in the exact same position last year and we've got three weeks now to get it right and prepare for the Scarlets and prepare for Europe.
"And that's the way it will be, a lot of hard work needs to be done."
While they were second best on the night with Pedrie Wannenburg's late double giving the scoreboard a flattering look.
However they were not helped by Italian referee Stefano Penne's interpretation at the scrum as he sent Declan Fitzpatrick to the sin-bin before awarding a penalty try to the Italians.
"When you look at the game, there were times when our set-scrum was under pressure," added McLaughlin.
"There seems to be a thing in the referee's book now that allows the opposition to stand up and you're not allowed to scrummage square anymore and the side that pop up and if you follow up after them you get penalised.
"Yes, we have to work on our set-scrums, there's no doubt about that but I think it also needs to be refereed fair and square and straight down the middle.
"Having said that under no circumstances is the referee at fault and we talked long and hard about our discipline; at the minute our discipline is a little off the mark but it's now a matter of us over the next few weeks that we eradicate the errors that we're making in the opposition '22'."
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