I tried to restrain a pug to trim one nail recently, and realized how stupid it was to do this right when I was about to leave the house. Because when I released the pug I was covered with a perfectly astonishing amount of hair, almost enough to require a complete change of wardrobe.
I believe that this is actually a defense strategy that pugs have evolved. Just the way squid can squirt ink to repel predators, pugs can release astonishing amounts of hair as a means of defense against attacks of nail-trimming and the like. We often see in nature that such mechanisms are exquisitely tailored to a particular opponent, and this is one of them - it only works on a species that cares what its clothes look like.