This is one of my hottest, hidden taboo fantasies, and up till now, Twolf's been one of the few I've told. We've talked about it before a few times.
It's so primal, and if I were coupled with a male dog, so degrading, humiliating, I would be so helpless and controlled. It's ALL extreme with this fantasy. The thought of being impaled, trapped by the knot, unable to be freed till the animal is done with me, is a very powerful image.
Have I done this? no. Would I? I'm not close minded to it, but no, most likely not, which is not to say I haven't had a fantasty about it (which I view no different than fantasies about scifi BDSM with aliens who have all sorts of strange and different appendages), but thats just it, its just fantasy. If I were to do it, I cannot say if I would still feel the same way as I do now. Some things should remain just that, a fantasy. However, find me a male human who gets a knot.. and i'm getting in line. Till that day, I am more than happy to be tied down and fucked senseless by a human Dom.
Is it abuse? It would depend on the situation. For example, if there's a female human tied up, so that she was open and the dog went and started humping her on its own free will, then no I do not believe it is abuse. However, I do believe that a male human with a female dog is abuse. She can't say no. The same goes for any human to dog oral interaction. Dog to human oral interaction, I do not believe to be abuse though. It's the animal making the choice to lick the human.
That's my 2 cents on it.