If there is a game-breaking glitch that destroys balance and fairness in the game, that is the fault of the developer, not the gamer who was clever enough to identify the glitch and utilise it - presuming this is done only by using the functions developers have provided them with in-game. If the consumers of the game don't like this glitch, then the developer is ethically required to release a patch to fix it, within certain unfortunate financial limits. If you as a gamer see someone else using a glitch to beat you, learn it and how to do it on demand, and show the other guy that you can play with code too. That'll show 'em.
Gamers who copy scripts from the Internet to increase their winning potential in-game are cheating. That's a no-no because it rewards you for something that took no cleverness on your part to do. If you can't win by cleverness in any shape or form then you shouldn't be winning. If you are, then you are cheating. Writing scripts on the other hand does take skill, if you're the original writer of the code, and you're good enough at coding to see an opening to break a game, then I suppose as an engineer you're furthering your talent to try it. I still would call it cheating if you overused it in online matches though, because it's unfair to others who don't have the qualifications to know the code.
Short answer: If it's in the game, use it. If it's a glitch people hate, get it fixed. If it's copied from the Internet then you're being cheap and are compensating for your own lack of brain mass. If you've written a cheating script itself, test it out, but seriously, don't ruin other people's gaming nights. That's fair play.