They apparently didn't follow the advice in their own brochure:

"Learn the special considerations for bear country. Contact the local public land agencies for advice and resources"- this is in their section on LNT principles.

I get it that firearms would be contrary to the conservationist ethic of the Sierra Club, and in general I am sympathetic to their principles. Polar bears, however, are a rather different breed of cat (or rather, ursid). It makes perfect sense to me to carry a twelve gauge in PB country, along with a full complement of slug loads - not to be used immediately, but available when necessary.

I understand that classically polar bears and native Inuit were in a state of mutual predation - "Let us prey" so to speak....