This is the sequence that completely changed the game: The Patriots were up 10-0 late in the first quarter and driving in Ravens territory. 2nd and 8 from the Baltimore 27, Ridley ran for 9 yards but it was called back on a hold on Gronk, replays showed no hold at all. Two plays later, Edelman caught a first down pass but was whistled for OPI on what was clearly DPI if anything (he was essentially tackled as he caught the ball). The Pats were forced to settle for a field goal.
On the next Ravens drive, the Patriots forced a 3rd-and-6 on the Baltimore 22. The drive was extended when the refs threw a flag on Jerod Mayo because his hand was on Ray Rice's back on an incomplete pass, even though he was within the 5-yard contact zone (it was a 2-yard penalty).
Those were the three most atrocious calls in the game by a long shot (in a game full of plenty of bad calls), and they completely changed the game. I'm confident that if you go back and watch the tape, they'll appear just as terrible as they did at full speed. The Ravens scored a TD on that drive, so it was at the very minimum a 7-point swing and probably an 11-point one if the Patriots scored a TD instead of the field goal.
Even if you want to argue that from that point forward the calls roughly evened out (which I don't think they did, but at least you could make a vague case for it), the game was already irrevocably changed by that sequence of events and what was on its way to being a Patriots blowout turned into a close game. Did they still have the opportunity to win in spite of that? Sure. And if they had, I'm sure I'd be less annoyed by what happened, but an 11-point swing in the 1st half is just as big a deal as one that happens late.