This is the “Pete Rose”’ school of thought. People defended him for years because he “only bet on his team to win” (and I’m not certain if that was ever proved to be true or just something Pete said a lot).
But that also has a negative impact. In Rose’s case, as player/manager, if he had a 3 run lead, he might bring out his best middle reliever who’d already pitched 3 straight games to protect the 2.5 point spread, putting a player at Heath risk, and/or making them unavailable for the next game. If Rose managed a meaningless game in August like it was game 7 of the WS, it might result in losing other future games that were less important to Rose, personally.
Likewise in the NFL. If you have a coach who’s winning a game 31-28 with possession & 4 mins to play, running the clock and trying to win 31-28 would be the way to manage that game. But what if the spread favored that team by 10.5? Now they’re gonna go for a meaningless TD to cover the spread? Lots of ways to lose when you’re trying to put a scoring drive together and don’t need to.
Betting on games is betting on games, regardless of which way one bets. Sure, throwing a game is an obviously terrible, immoral course of action. But it’s no more noble to bet on one’s team to win, and it can absolutely have a negative consequence.