I don't really mind infinite money cheating if you're struggling with a game due to difficulty or balance, but there's nothing difficult about Animal Crossing. Money functions as a pacing mechanism and a barometer of dedication or cleverness, and giving yourself arbitrarily large amounts of money duping rare items fucks up the former and takes all the thrill out of the latter. It's not like there some sort of Region First achievement for getting a complete set of gold furniture; you don't need golden tools in order to be competitive. Your friends aren't going to yell at you for visiting their towns with less than perfect gear.
But hey, if these people want to play the entire Mario game in the golden tanuki suit, I don't have a problem with that. Personally, I like to feel accomplishment when I'm done with a game, but it's their game to do with what they want.