I have to contribute to SB's theory.
When I was a kid, I went to the arcade. A new game had been installed. It was called "Mortal Kombat". At first I thought the game was cool. Every boy in school was talking about it. One day when the arcade was somewhat empty, I decided to look at a guy playing MK. He was playing as Kano. It was then that I witnessed my first fatality ever, Kano's infamous heart rip. I was TRAUMATIZED from them on. I had never seen something as gruesome. I then kept seeing worse stuff, like the head rip, the explosions, the infamous pit (complete with decaying bodies) and characters being burned to a crisp.
The images were burned in my mind forever. It got to the point where I wanted to avoid anything MK, which was hard to do because everybody loved the game. It was till MK 3 hit that I grew up and realized that the violence was stupid and out there, so I grew to tolerate the series, then enjoy it.
Even if I grew up and became "decentized" towards game violence, the terrors I went through after I saw such brutality as a kid are still fresh in my mind.
And for the record, I always found the Itchy and Scratchy segments disturbing as hell as a kid, along with the Halloween specials (its a good thing that the infamous inside out dance sequence happened when I grew to tolerate blood and gore, otherwise it would've scarred me for life).