Dogs are usually trained to do what humans say, so the dog is very likely just doing what it thinks is being asked of it.
Completely situational and that assumes a lot. You have no idea if this is the case even 20% of the time. Much less the majority of the time.
Even if risk was only 20% that's still too high imo.
You cannot infer that it is actively consenting.
Legally we can infer consent from action alone.
"implied consent n. consent when surrounding circumstances exist which would lead a reasonable person to believe that this consent had been given, although no direct, express or explicit words of agreement had been uttered. "
That only applies to humans because humans are capable of giving express or explicit feedback to the contrary. Animals cannot so you can't infer from their behaviour because there is no way to verify your interpretation is correct. With humans it can be verified.
Also you don't know if the animal is being threatened or abused off camera to force it to act in such a way.
You don't know that when any two people have sex on camera the same thing is going on. Ban porn!
Again, humans are more capable of objecting or challenging others when they are being abused. And yes I'm a fan of employing practices to eliminate trafficking and abuse in pornography. That's another discussion though.
Humans can communicate with each other whereas a dog cannot.
A lot of dog owners and trainers would argue otherwise. You mean through words. Words aren't necessary, you just want them to be. Words aren't even necessary for consent among human beings when it comes to sex.
Words aren't necessary for humans because they have the ability to use them if necessary. That is, if mistake in interpretation was made, humans can alert to that fact. Animals cannot. However, even if implied consent was acceptable then you're relying on people to accurately interpret behaviour. Most people interpret things how they want to, so again it's not going to be a reliable interpretation necessarily. That is much harder to police and enforce than the rule "no sex with animals". Especially given the fact there is no compelling argument that humans need to fuck animals. Or that any conceivable benefit of allowing it would outweigh the many risks and scope for abuse.
I'd rather err on the side of caution and not condone bestiality.
I think that's more because you don't like the idea of people having sex with animals, rather than you're worried about consent. Otherwise you'd be making this out as an issue of rape (no consent) than an issue of "bestiality." If adult animals can have sex without harm and humans can have sex without harm, there are going to be situations where animals and humans can have sex without harm. It's not 100% always rape unless you require verbal/words for consent which is no a legal standard anyone would ever require.
It is an issue of rape. I never said it wasn't. But it's also got other elements that human rape doesn't have, like the inability to communicate effectively. And yes ideally, words would be used where possible to confirm consent. Also, you are right. I don't like the "idea" of having sex with animals. And 99.9% of society agrees with that so it's not an invalid feeling.
Just because humans can fuck each other without harm and animals can fuck each other without harm, it does not mean interspecial sex is okay. There's a massive power differential between humans and animals (humans being the ones with the power) that makes it intrinsically abusive and manipulative, even if no obvious sign of harm is there. This is similar to why sex play between same-age kids is accepted as part of healthy development, but kids and adults cannot do the same because there is a power differential makes it inherently exploitative.
Anyway, I'm done here. This is going around in circles and I'm certainly not going to be persuaded to change my mind. I'm happy to be closed minded towards bestiality. Ain't nothing I'm losing by taking this stance.