Deer browse our Washington hawthorns at camp. But they only seem to browse the newer growth - the parts without thorns. I don't see evidence of them sticking their faces into the thorny spots to chew. I caged ours until they got to 7 to 8 ft. tall and the majority of the canopy was out of harm's way. They still nip the lowest limbs - at the tips for the new, tender growth, but it has no effect on the trees.
The red berries they produce are favorites of grouse & turkeys, as well as other birds in the fall & winter.