When we had dogs that went on our bed, we covered all the bedding over with a waterproof mattress cover and a top sheet. One obviously has to choose between aesthetics and allowing the dogs on the bed. So his choices are, let the quilt be ruined, cover it up or hang it on the wall. That's what I would tell him.
With respect to the hanging, I would not consider a quilt being hung as 'not be being used.' It is being used in the way he wants to use it, and being appreciated. But advise to hang out of direct light.