It's pure speculation, not that I don't ever engage in it and think it's certainly a topic worthy of speculation. We all react differently to these substances and can have the effect of speeding up, slowing down, or otherwise altering our perception of tempo and tonality. I've had some pretty crazy experiences some turned out musically ok others did not. I try to have a policy of not doing something like that in front of a paying audience as they deserve more for their money than a crapshoot. Free parties on the other hand . . . all bets are off.
If Bobby did this to himself, hopefully the lesson will prevent it from happening again in the near future (of course, as memory fades we tend to forget these lessons and need a refresher). If someone did this to him - shame, shame, shame. You should never give something to someone unwittingly. The person owes a lot of people who paid good money to get into this show. It is incredibly selfish and stupid - not what this scene should be about.
I went to a couple hundred GD shows from 82-93 some were awful, some ok, many were great. I'd give them a pass on a singular incident. If it becomes a pattern I would quit buying tickets as I did in 93 when the music no longer met my standards for paying $50 and driving a couple hundred miles.