No, there's no way to turn it off. I looked through the options today, and nothing. I personally like it, but I have a morbid fascination with the effects of weaponry on the human body. (especially in a gaming sense)
I played the kill Hitler DLC today. It was OK fun. You get plenty of enemies to snipe at and a tank to blow up. I blew Hitler's nose off in the end.
I was quite happy with that shot. He took off running for his train, and I just brought the rifle up and took a snap shot with it on the lowest magnification.
Played it again and went for a nutshot. It hit him in the groin area but oddly missed both the onions and the corn.