A domestic animal is quite a different thing from a captive animal or even a tame animal. Fenris is not dead, merely bound. There's a permanent conflict between the bidding of our instincts and our society and, though most of us see it as necessary, we can't but resent it. This leads to perversion, which to me is performing an act because it's taboo as an act of defiance against God, Society or conscience. In other words against our domestication.
Perversion can be harmless or liberating.
It depends on whether the taboo defied is really necessary. However in the perversion of crucial taboos, for example against murder, lies the origins of Evil as a motivating force. People tend to thing that evil acts are undertaken for some gain, slipping through the net of conscience. Of course many criminal acts are, indeed, in that category but some acts defy that kind of analysis. Sometimes there's no imaginable gain and even rationalisations in terms of the feeling of personal power start to look decidedly threadbare.