Doors. Peter Parker hated doors. Why does Peter Parker hate doors you ask? It's solely because Peter Parker is an idiot.
Of course, this doesn't really narrow much down, so, for your sake, I'll go into more detail.
Peter had been out with Ned and MJ. Peter wanted to show them this cool store that had just opened that he'd noticed while out patrolling. Somehow, Peter hadn't sensed (so much for the Peter Tingle) that there was a door to the store. As absurd as this sounds, it's Peter Parker, what did you expect?
He walked straight into the door. Which MJ, of course, caught on camera. Embarrassed, he went to open the door. Here's another thing about Peter Parker; he's oblivious as hell. This door, was labeled, in bright green writing "PULL".
Yet, Peter Parker, being the loveable idiot he is, pushes.
"Maybe the store isn't open." Peter thought to himself, while continuing to push.
If Peter were any normal person, he'd have tried to pull by now, seeing as pushing wasn't working. But we all know Peter Parker is anything but normal.
Ned watches Peter desperately push on the door. He's trying so hard, and Ned doesn't have the heart to tell him that, not only does the door say "pull", but everyone inside the store is watching with amusement.
MJ, still filming, shouts "Maybe you should push harder."
He gets tired of pushing, and turns around, when MJ swings open the door with a single pull. "I opened it loser. So much for super strength." she teases.
Later, MJ shows the video to May. He's never seen May laugh so hard.
This is why Peter hates doors.