I'd say, the way Ingus was acting, his time was short anyway. Imagine if he got targeted by Mafia and the Vigilante or Serial Killer targeted Edgar, who if you'll remember was having a negative back-and-forth with Ingus. We find Edgar's body in the morning, suspect Ingus of persuading the Mafia to kill Edgar, and end up lynching him the following day.
This turn of events, however, produces a similar outcome (with Edgar still being alive of course) and reveals to us the fact that there are other roles with nightkilling power. This here makes the game far more interesting and dangerous for all of us.
That being said, since Ingus was probably going to get lynched sometime in the near future, it probably wasn't the best use of a nightkill. Then again, it also prevents the Mafia from growing in size by recruiting Saulus, so it really has positive and negative impacts for both sides. I'm as confused as Rinoa and Fran are.