While I agree that having Discord should be innocuous, a parent who has no idea what Discord is should know that it could be used to talk to (potentially dangerous) strangers online.

A simple "Hey (son/daughter), the police told me that if anybody on Discord tells you to download LOIC, then you're probably in with the wrong crowd" is what I would hope would come of this (along with the typical internet stranger danger shpiel).

I also am scared of the worst case scenario you present, but this brochure doesn't seem like that to me.