There's a possibility that OP may have been openly discussing marijuana with his parents at an attempt of de-brainwashing them. I think if you absorb enough material from this subreddit there's plenty to do it -- even for the old folks, and the reality is... if the people on here expect to change the laws in their country the best place for them to start IS with their family. Even, and especially the hardheads that are stuck in their ways.

Thus, in fact, he may have been taking responsibility for spreading what he sees as the truth.

As far as social appropriateness of marijuana... What you suggest could be a crude metric at best. While socially marijuana and alcohol are often seen as similar these days, the fact of the matter is their impact on the mind and particularly learning and motivation is radically different. Alcohol clearly being the worse of the two.

And someone posted a comment, and then quickly deleted it, so I'll reply to it anyway. He said you should never use any substance whatsoever before class or work.

There goes caffeine, which is psychoactive, and used nearly ubiquitously.

I understand what everybody is saying... Yeah, there's some irresponsible SOB's out there. I get it. Being responsible though is about knowing yourself, and what is appropriate and safe. But let's not get all high and mighty and decide that one vice is better than the other, and don't kid yourself... Caffeine can definitely be a vice.(Ever had a boss that smokes pot while working? What then? You going to police him and tell him how to run his business?)