Qzz-
Like purplegirls says, one obsession sometimes becomes replaced with another one, but you can't avoid intrusive thoughts by avoiding the television.
I have a very simliar problem with the tv, as I'm sure alot of us on the board do. We avoid the tv because if we do that or change the channel right away, we'll be spared seeing all the bad stuff on the 11:00pm news, which in turn helps prevent us from having an OCD moment. The only problem is you'll eventually start to find something bad in anything you watch, even if it's Barney. If you really think about it, it's hard in todays day and age to avoid bad stuff because everywhere we look, we see violence, pornography, degredation of women, so forth and so on. The whole key is not to avoid the tv and practice exposure thearpy for a small amount at a time.
Basically the way exposure therapy works is you expose yourself to the situation you're most afraid of for a very small amount of time to begin with, then gradually increase the time as you go along. The same principle that works for exposure therapy is the same one for systematic desensitization, or when a Psychologist wants to help someone conquer a phobia.
For me, whenever I see something on the tv like a graphic movie, I'll just tell myself, "it's just a movie, and it's not real." If it's the news, I'll just say, "that's too bad, and my prayers go out to the family." If it's something like you watched that has to do with a murdere, I'll say to myself, "I'm glad I'm me and I'm normal." That's all I do and it works pretty well.