Evil seems a bit strong. I doubt there are many people who can be said to be completely evil, whilst I doubt there is anyone who can be held up to be completely good. Gandhi saw no harm in Apartheid (just as long as it didn't apply to him) and Mother Theresa made jokes about the pain and suffering of others she so delighted in as a measure of God's Love (the famous 'Jesus Kiss' routine she regularly featured as part of her stand-up act). For sure shit happens, but I've known the most decent of people do the most appalling things, and vice-versa if I'm honest.

It's true though - the good stuff outnumbers the bad to the point that the bad is exceptional to the general rule. That the negative stuff draws our interest is simply because it is the exception. People need the story, and invariably respond with stories & ballads of their own. As I recall, the case of Raoul Moat provided a plethora of both - a latter-day Staggerlee indeed.   

But, just as Pornography exploits our Sexuality (and Religion our basic hopes & fears of life & death), so the Media exploits our darker curiosities. There was a case when this chap went to the doctor because he was depressed about the state of the world and thought some pills might help him better cope with it.
'What makes you think the world is so bad?' asked the GP.
'It's all I ever read about in the papers - all I ever see on TV,' came the reply.
'Then might I suggest you stop reading the papers and watching the TV?' said the medical man.
And so the depressive was cured.