What happened during the lesson afterwards? Did you watch the class? Was the lesson degraded, did the teacher lose coherency? Was the rest of the seminar a waste? Were people injured? Did the students ruin the lesson for people who were on the mat? Were people aware of what happened who didn't witness the conversation?
what about going to class sick, or injured? what about angry or emotionally distraught? what about taking cough syrup, or methadone?
what about HIV in the dojo?
What happened concretely?
personally I think it's waste of pot to smoke pot and go train. Focus in practice will anull the high .. you get to a different space; one which anyone who practices regularly reaches without being stoned anyway. Practice without focus and you're wasting your training time.