Personally, I am against hacking 31 IV'd Pokemon. I'd rather have an entirely legit Pokemon that was bred entirely by myself, no outside help needed. I like personalization. I would only allow myself to do it for a Pokemon that I couldn't get otherwise (a legendary, like Lugia or Mew), or Pokes that I can't SR for anymore (Cressy and Azelf). And even then, I wouldn't let myself put 31 IVs in any of their stats.
I'm not against cloning, however, as that would make me a huge hypocrite (I love Emerald to death). And hacking items and TMs seems fine to me.
I guess I wouldn't have any problems fighting someone who hacks, so long as they kept within the game's limits.
/(BAN ME PLEASE)ry