This is not all true. Degradation if that is your only motivation can be further satisfied in looking up things like rape, scat, beatings, insults, etc. When it comes to zoo depends. I would imagine a video showing for example a woman taken by a pig and dragging herself through the mud to suck not much of a unit would be much more a hit amongst people enjoying to see women degraded, also because of the image of the pig in mainstream society and many cultures, as unclean, dirty, etc
When you see a woman being taken by a dog or a horse or sucking massively big units, etc. these give a sense of virility and power physically superior in stamina to men, and it has to do a lot more with primal instincts and taboo (ie: beauty and the beast, hunter and the prey, etc) So I would say people watching these vids, they appreciate maybe an element of degradation, but it is not their main object of desire