From what? Themselves? For years they did little to preserve their intellectual honesty, and opened their membership to anybody who did not represent the conservative movement in this country. No card-carrying Republicans need apply. After all, those were the people who would denude the mountains, dam and divert the natural flow of snow melt, hunt down wildlife to the point of extinction, and throw away Styrofoam coffee cups on the roadside.
So the Sierra Club is under threat from some of the radicals they freely invited in. Some 95% of all the woe in this world is self-induced.