It was a legitimate question. This is a children's cartoon, so one wouldn't expect them to casually reference drug use. No need to be a jerk about it.

Okay fair I thought you were just pointing out the obvious. As for your question: they don't technically reference a drug at all with any of the hippie ponies. While they do act like there stoned, it is possible to have a "stoner's personality" without useing any drugs. the hippie pony have been scene in the comics and there was no ishue with them there.
Personalitys technically are safe. Since the hippies are portrayed as druids in there universe then its as safe as the lorax.
There were much more risky jokes including things relating to nudity just on this show.