I'm not the one throwing out "darkening the soul," but here we go:
If you want Andrew Vaughn to hit a home run, that's going to negatively affect a pitcher's possible career. Maybe it extends an inning to the point where they narrowly miss out on an All-Star game, and thus financial bonuses.
If you want Crochet to strike out a rookie making his major league debut, maybe that rookie gets stuck in his head and gets sent back down.
If you root for the Sox to win the division, you're hoping for the other four AL Central teams to do poorly, putting the careers of their front offices and coaching staffs at risk.