Alright, so it seems like most people agree that scooping is okay, whether they would do it or not. However, here are a couple somewhat more difficult situations for you guys, which I've also encountered before.
First, suppose you're borrowing two of your friend's Mewtwo-EX's because your deck needs them but you don't have any of your own. You get paired up with him and beat him fair and square. Do you scoop to him because you're using his cards?
And second, suppose you make a terrible mistake that will result in a game loss (like playing two shuffle supporters on the same turn). Your opponent lets you take it back and fix it without calling a judge, so you can continue playing the match. After the match ends, you win. Should you give them the win because you should have lost? What if it was a different kind of misplay that doesn't break game state but would still lead to a loss, like announcing Outrage instead of Bolt Strike?