Yeah, this game is going to have several frightening parts.
You get used to it. The game is awesome. Just remember:
The doctor is behind you!
Seriously though, are you just now getting the game? That was easily one of the best games I ever played. Absolutely exciting, tactical, beautifully artistic, thought-provoking, badass... the list goes on and on. I love getting new weapons. Nothing feels better than first getting the shotgun, or the napalm launcher, or the grenade launcher, or the crossbow.
By the end of the game, you're packing more heat than a fighter jet.