Why do some want to ban what they call "trolls"?

My eyesight is still good, Homer. And I have been doing what we were warned would blind us for many, many decades...Heheheh...

Actually the REAL 'trolls' are Niceass, Wiseguy, Jimjazz and J23.
Personally I think they're ALL the same person....
Again people PLEASE go out to clubs and masterbating to free porn! - "you'll go blind".......

I don't understand why some want to ban the "trolls" - without bad guys you can't have good guys and vice-versa. Besides, who's a "troll" or not a "troll" is a matter of taste, not fact.