While I understand (and often share) your cynicism, change.org has won some victories in the past: http://www.change.org/victories
The level of the "victories" do vary. But, in this particular case, I think a mass expression of support for this girl could actually encourage the local DA and school reconsider moving forward with prosecution.
Perhaps steer clear of questioning whether he was correct to guess your meaning when following it with a line that confirms you were indeed being cynical. Not saying you are wrong to be cynical, but you are (as am I).
The level of the "victories" do vary. But, in this particular case, I think a mass expression of support for this girl could actually encourage the local DA and school reconsider moving forward with prosecution.