Those scenarios aren't really comparable penguin, if a horse is conscious and chooses to mount a presenting human female it does so of its own free will - you can't compare that with an unconscious person with an erection.
Sure you can. Capacity is present in both situations; heck,
choice and action may be present in both... but consent is not necessarily present in either.
By trying to compare them it suggests that any and all actions undertaken by a horse are not of its choice, that everything it does is the result of something/someone else taking advantage of it, which I think you'll agree is ludicrous.
No, I'm saying that regardless of whatever decisions makes, a horse lacks the capacity to consent in a way that makes it okay for a person to have sex with it.
The point is that, if I take the initiative, and mount someone or something, then that is me giving consent. If a horse does the same, it is the horse giving consent. You're right that the ability does not imply the capacity to consent to the act, but the conscious, non-coerced decision to perform the act does imply that. Here you seem to be saying that no act a horse performs is its decision. I disagree with that.
No, I'm saying that a conscious, non-coerced decision to perform an action only implies consent when the person or thing making the decision is capable of informed, intelligent consent.
The key point that I think you're overlooking is the fact that the horse is doing the action of its on will. The person is not threatening it or anything. The horse chooses to mount the person.
For real consent to be present, the horse would have to be reasonably aware of the potential consequences of its actions and voluntarily accept them. To establish that the horse consents, first you have to establish that it has the intelligence and self-awareness to do all that.
You mean of "assault"? I am not disagreeing with that, but "assault" seems like a harsh term for the act you describe on the plane. I agree that it is wrong, and it even qualifies as "assault", but it just doesn't seem to fit how I think of that word.
I don't know; I'd consider it assault myself, but I just took the term from the law.