a dog is not worried they will be left at a pound of they don't mount the human that is in a ready mating position.
No. And you should stop being so explicit in your discussion of bestiality if you want people to address the core of your argument.
Dogs are literally conditioned to be highly dependent on humans. Their moods, experiences, and entire well-being are dependent on an owner. It is the absolute most explicit type of Stockholm Syndrome there is, considering dogs lack abstract thought to the extent that they don't even pass the mirror test. They complete capable of grasping even the concept of selfhood. Something without a self cannot consent.
If this argument were true, it invalidates all pet ownership and human/animal interaction. After all, how do you really know if dogs consent to fetch, play fighting, or cuddling?
It may actually do that. Is it morally right to own an animal which might benefit from your ownership but is incapable of a choice in the matter? This is a complex question, but not one that's the same as "Is bestiality okay?"
Sex within ones own species is okay. In fact, it's a biological imperative to continue your species. It's not the physical safety of humans or animals I'm concerned with, it's the impact it may have on humans, and the fact that animals are unable to consent. Humans without impairment can consent. We don't even believe drunk people can consent. How can something without a concept of self consent? It's impossible, that's where they'd be on the level of impairment. If you believe it's wrong to rape a mentally disabled person because they have an IQ of 40, it's also wrong to perform bestiality.
All an animal cares about when it comes to sex is their mate choice is nice to them, meets their desired requirements, and makes them feel good during the act.
You do not know that because you are not psychic and animals can't speak. And many, many animals experience painful sex even within their own species.
It's humans that have a convoluted and arbitrary view on sex. Look at how long we persecuted homosexuals for. Other animals don't do that.
Because human sexuality is complicated, we have these discussions. We're not base animals, we're capable of understanding nuance and right and wrong.