The dangers of petrol are a total non sequitur in this case, and have no bearing whatsoever on the well-documented and well understood dangers of hydrogen gas.

The dangers of petrol are a total non sequitur in this case, and have no bearing whatsoever on the well-documented and well understood dangers of hydrogen gas. Cholesterol is likewise highly dangerous, but saying "far more people die of heart disease than hydrogen gas accidents" has very little import in a discussion on airships and helium. There are good reasons we don't use hydrogen anymore in airships and use helium instead. There are other good reasons not to use helium, but those reasons don't trump the dangers of hydrogen, unless you knew of specific development which would mitigate the dangers that pressurized hydrogen gas presents, which I'm guessing you do not.