I agree it was heartless - youngsters can be reckless and thoughtless. I hope he makes a full recovery and wish him well for the future.
I certainly don't wish harm on the lad, and too hope he makes a full and fast recovery. However, whilst the "no one made him jump" comment was a bit heartless, it's nevertheless true.
Reckless and thoughtless is trying to jump over the canal at a section where the worst that will happen is you get wet feet, or overshoot into a bush on the far side.
Trying it where the worst that can happen is you fall 90m down into the valley is just stupid, plain and simple.