I wouldn't go so far as to say we NEED to experience the bad to know the good, but I think that in life it is inevitable that we will experience some bad events and that those experiences have the potential to change our perspective in a beneficial way.
I also think we are talking about PERSONAL experience. Reading about a poor girl shot in the back and killed is not the same as being there when it happened, seeing her bleed out and turn cold, and it certainly isn't the same as being her.
My wish would be that no one should experience bad things, especially me. But when we do, i hope we have the fortitude to demonstrate the honorable oriental saying, "falling down seven times, getting up eight."