Personally, I see nothing wrong with using cheats/save-edits (or in my case, glitches) to take on the PWT/Battle Frontier/etc. It's not really an unfair advantage. It's more like evening the odds. If you go to the Battle Factory in Generation III/IV, you can see the rental Pokemon suck horribly at first. They give you the wrong Pokemon with the wrong IVs, wrong nature, horrible EV spreads, and terrible moves. But as you progress, the rental Pokemon become better and better until you start seeing Legendary/pseudo-Legendary Pokemon with good natures, IV 31 all, efficient EV spread, and great move pools. It's like that in all the battle facilities. Which means, if you don't have IV 31 all things yourself, you're at a disadvantage to start with. Not to mention the AI will cheat against you. Hax, as it's called. Your Flamethrower will miss because of their Brightpowder. Their Zap Cannon will hit through 5 Double Teams and land a critical hit. So against the AI, using cheats (or Jolly No Guard Machamp with Sheer Cold) is merely evening the odds.
Against human players, this changes. When both players have the same success rate of their attacks hitting, cheats and such become... unnecessary. Some people don't care about using hacked Pokemon, as long as the Pokemon's stats, moves, etc are within normal ranges (as in, if you use AR to trigger the Azure Flute event in Platinum and catch the Arceus normally and use it against me, I wouldn't care). Some people don't care if you use Pokemon with glitched movesets. Some people, however, do care greatly about hacks/glitches, so it's always best to just... know the person you're battling ahead of time. There are some people who claim that RNGing is cheating (which it's not, says the RNGer...), and won't battle you if you're an RNGer. So some people are a lot more lenient than others, so it's hard to say what's accepted and what's not. It varies from person to person.
I like to think I'm one of the more lenient ones. I don't care if the Pokemon I'm facing is shiny with IV 31 in every stat. I don't care if it has moves that it's not normally supposed to have. And I don't care if the person I'm facing uses cheats in their games, as long as the end results could be obtained without cheats. Meaning, I don't care if a person uses AR to create a shiny IV 31 all Pokemon if they already know how to RNG.