First, the study I referred to earlier is fairly well known by outdoor people who have to deal with the risk of bears but do not have a pre-existing affinity with firearms.

--- This is their world view. You could say they have a pre-existing dislike with firearms too.

I've heard this study referred to both by in online forums as well as in real life by my wilderness first aid instructor who was involved with the gun vs. bear spray debate with his SAR unit (he was on the bear spray side).

---It is not a vs. situation. Choosing one over the other is kind of like choosing whether to have airbags OR a seat belt in your car.

The second reason is training. To send a group of people with no prior firearms experience out with guns but no training is (I'd hope) a non-starter to begin with. If a program were to provide firearms for protection they'd have to provide a decent level of training first; something I assume this group feels falls well outside its mandate.

---Bet most of them haven't used and ice axe either. They are dangerous if used incorrectly, but you
can be sure they train and carry them on glaciers. If their
mandate is to travel in the Alaska wilds, they also have a
mandate to protect the students as well or better than the
local population protects themselves.

This second point links in to the first point: if you are convinced bear spray is more effective in repelling an attack than a firearm then your risk management strategy doesn't need to incorporate firearms; on paper they become more liability than benefit.

---It is no longer on paper. Green ideology comes up against
children's safety.
If omitting a firearm component makes the students
less safe than similar groups traveling in that area
(fishing guides, NPS, NFS etc.) they are leaving themselves
open for criticism, or worse.