FNAF 4 isn't violent. The games never intend to be. Sure, The lore and what happens may be on the horror side but it's a horror game. A violent game would be GTA 5 because it's more on the shooting type of game whilst FNAF 4 & the other games are more on a mystery horror.
The games don't intend violence, Besides the bite mini game and the actual lore behind it. Scott Cawthon (FNAF'S creator) doesn't make quests or objectives to go and kill someone, However in GTA, You're shoved in with a gun and told to kill someone.
So to speak, No FNAF 4 isn't too violent.