pot parties have been popular with kids for decades and they really don’t seem to be causing much harm.
It’s not the pot smoking itself that displays the harm. Usually all that happens at the time is a relatively peaceful stupor. And if that was it, the concerns would be less. It’s what happens in the longer term as a consequence. THC is not just there and gone; it lingers (brains are largely fat).
This stuff might be the best thing since Jesus’ healings for treatment of severe and chronic pain for all I know, and that’s wonderful if it is and patients should not be denied it, but smoking it gratuitously is an abuse.