Given that professional wrestling is built on the entire premise of creating the illusion of hatred where there is none, the curtain between backstage and front is sort of imbued with mythical powers. Cross it, and no matter how much you like someone in the real world, it's time to go out there and batter them as if your life depends on it.
Thing is though, that works both ways. No matter how professional you're trying to be inside the ring, once you get backstage then all bets are off. Any smiles that were there for the camera get dropped, and any responsibility to put your opponent over goes out of the window because, if they've done your dirty, you're going to have to let them know.
This business is no stranger to a bit of backstage beef, and indeed there's now an entire industry built around the money that's to be made by giving wrestlers a microphone and letting them get it all off their chest. Thankfully, this makes for some incredible stories, all of which add to the legend of that small piece of black fabric, and how men were prone to explode the very instant they got behind it.