I think that if he owns the game, and it is his, and his alone (meaning no online), then he can hack to his hearts content. it shows weakness really.. most people have a small set of rules or morals for hacking, and mine are as follows:
never hack a new game
never hack an online game
after beating a game once, start looking for glitches without hacks
After completing everything you can think of doing, and still want to play more, but without rules and hassles, then why not?
If you are online in a game, and it's loaded with hackers, like Phantasy Star Online.
Hacking is best to avoid, but if you must to stay safe, use minimal hacks. no Character changers, no invincibility, none of that.
I am for using glitches though. Any and every glitch that does exist, I will try and find, and use.. not abuse, but use. (for example, if there's a glitch that gets you money, only use it when you absolutely need money)
Anyways, that's my say.