While I think there was a lot of failure to go around, the group leaders should know better.
What makes you think that?
It is an aspiration -- not a description.
I think that whenever someone assumes a leadership role, there is an ethical/moral responsibility that goes with that role to take some minimal care regarding the safety of that group and the individuals in the group. It doesn't matter what the group is or why it was formed. It is true that many people -- probably more than most, who are appointed group leaders don't think about such things. IMO, they should. That's the aspiration part.
Using this incident as an example, I don't expect the group leaders to be experts in survival, or even near that, to take a group out on a hike in the park. But I do think that it is part of their responsibility to think a bit about things like the weather etc., and remind people to take a jacket etc. with them.
Exactly what steps should be taken by the group leaders have to be based on the facts of the situation---but I do feel it is always something that should be considered. A few reminders before the trip might have saved a lot of discomfort.
All that being said, it still doesn't eliminate the individual's responsibility to be prepared.
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