Elliot's letter to the student body was extremely powerful and moving. He had several reasons to write it, and it had many strong points. But I believe the main thing he wanted to get across was that awful bullying happens quite a bit and it quite possible to make bullying just a small problem, but in order for that to happen many people (anybody) have to help.
The letter Elliot sent out to the student body really made me think of how much courage it takes to take the victims side. I think partly because I read all this and it sounded so straightforward and simple, yet bystanders standing up for victims is increasingly rare. Although the quote was in a fictional story, I think some of it can touch bystanders everywhere who read this book.