I do not think TV, computers, games, candy, etc. are inherently "bad." BUT, I absolutely know they are addictive. Maybe not to everyone, but for many of us, yes.
This is what we do-- for TV, we have a DVR. We only record certain shows, and they have to skip past commercials. My guideline for TV is that they should not watch it only because they are bored. Want to relax? Sure. Want to learn something? Yup. But doing it just because they have nothing else to do-- no. This is where you step in with ideas. This DOES NOT mean that you have to be your son's playmate. I think many adults are uncomfortable with this because it is not what we are meant to do. We can be playful with children and play with them, but I do not think we should be their playmates. Plus, sometimes, children should be bored. Why is bored a bad thing? We can't see it this way. Even though I was not an only child, I learned to play a lot on my own. It is a good skill, to be able to hang out with yourself. You can learn this by being bored. By accepting boredom, we also come to peace-- to see that we do not need to be entertained every second. Isn't that a nice freedom?
For the computer, we have a timer. They can play games for 30 minutes (we give them choices) but they can use the computer other times for writing and drawing. That does not count for the 30 minutes. One thing they LOVED was when I gave them tickets. You could do this for your son. You could give him screen time tickets-- whatever limit you set, and then in 30 min. increments or whatever. He could apply them to TV or computer. They love to cash in those tickets!
So, they do have access, but there are limits in terms of content as well as time. Like you said you don't like the fighting on TV-- neither do I, which is why I would never let my children watch shows in which there is violence. (Well, not the young ones-- older DD has read and seen HP movies.)
Oh, and something else they like-- they like when I watch TV with them. We talk about the shows. I actually like some of them! Not only do I like some of the kid ones, but they watch some meant for "everyone" like Nature (they love this show). ..and they will watch Globe Trekkers with me, too.
Really, I wish someone would set limits for ME. I always did my homework and was "responsible" but I watched waaaaaay too much TV. No real limits. Now I have the task of trying to do it as an adult (set limits) and I think it is hard. I love when we are on vacation-- even though DH always brings a laptop, I steer clear and enjoy my time away from it-- I do not use it at all!