The reasoning in the article is laughable:
It’s a bad idea — if for no other reason than it cracks open the door for other changes that violate the spirit of the Wilderness Act. If you say yes to mountain bikers, how do you say no to mountain skateboards (yes, they are a thing)? Or to hang gliding and parasailing, activities that also are excluded from wilderness areas? Or snowmobiling and power boating? These lands were not set aside to be playgrounds for humans, but to preserve their continued existence as wilderness. Besides, wilderness areas account for just one-sixth of federal public lands, leaving plenty of other outdoor space for biking and other forms of human recreation.
That IMBA is against this too is ridiculous and simply a political maneuver that seems more like fighting Trump than anything else.