I'd rather break a slug rack than go through all that effort of racking after a win. Not racking is the reward for winning. Loser racks, and slugs beget slugs. My rack will always be as perfect as humanly possible for an opponent. If they don't respect the game enough to return the favor, then I stop caring how their rack is as much. I won't intentionally slug them but I sure won't show much care if I'm "gifted" a slug.
Ironically (and probably stupidly) I pay more attention to getting a perfect rack for my opponent than on rack your own. Balls will break either way, you just gotta adapt to the rack at hand. In a tournament, I'll look at the rack if my opponent racks, but I won't say a word. I'll break it accordingly. Pool is a mental game. Use the energy to your advantage and don't just stew over it.