That's a large leap; all analogy is suspect, but you missed a bunch on that one; I guess I'm fine with him doing high risk flying (low level, steep turns, while somewhat chemically impaired) if he's doing it with low-to-no real risk to others. You and I both know that's not the when case drunk-driving, unless it's on a deserted highway, or on the Salt Flats, etc.
So, his choice, as it is certainly yours to consider him foolish, reckless, etc. I'm not gonna fly like that, but, again, I'd prefer to have the option to do so, vice having restrictions imposed by folks I don't share values with. I've never heard someone say "I wish they'd make a rule to stop me from doing X" . . .
I don't know if the chems were a causal factor or not - my intuition is they weren't, presuming his tolerance might have been higher than the average bear. Pretty sure he did/did know he intended to fly, in whatever state of impaired (or non-impaired) faculties he experienced. I'm sorry he was killed, but I like he had the option to manage his own experiences, however misguided or risky the rest of us considered them.
That said, If he was my friend or acquaintance, I'd have talked to him about pulling back on it. Once: "That's high risk activity, Bud; I hope you're thinking about the consequences - you have a family, etc."