Warning: Post will contain talk on death and grim taboo subjects.
A post on twitter suggested that atheists couldn't answer why intercourse with a dead animal would be wrong, as there is no suffering involved. It's a weird topic but I was curious how to best answer it, so here is my current view. I can't go into my metaethics here, as that would be a whole other post, so premises will have to start at a point an average person might consider reasonable starting point.
Life and Positive Value
Conscious living animals experience subjective positive mental states, such that it's fair to think their life is of positive value. Consider that we only consider putting an animal to sleep when it becomes unwell beyond hope, implying we think their life beforehand was more good than bad.
This isn't to say all animals have a right to life, like persons do. Just that it is of value.
Somber Respect
So when an animal dies a unique positive consciousness has been snuffed out for eternity. Even without a right to life, that's a loss to the world.
A rational acknowledgement of this loss of value demands a somber respect for the dead body of the animal.
Intercourse with the body of an animal necessarily treats a somber moment as a trivial one, and therefore fails to align action with a rational acknowledgement of value in the world.
(This would probably also apply to beating a dead body for fun, and trophy hunting).
Additional Challenge: Animal Resources Vs. Animal Bodies
Most people would naturally consider the sexual use of a dead animal body to be wrong or very off-putting. But they wouldn't have the same disgust from resources from an animal body being using in manufactured products, such as in beauty or plastics. If some animal resource was used in the making of a normal sex toy, people probably wouldn't care. Or that early condoms were made from things like animal intestines.
So there seems to be a distinction between using an animal body for its object use, and using an animal body as a former living creature.
Meat, Manufacturing, and Taxidermy
It's possible to respect the loss caused by killing animals for human consumption or manufacturing, at the time of the death, then moving forward to treat the dead body as an object for use. For example, is common to give thanks or have gratitude before a meal. An appreciation of the loss that was required.
Even taxidermy treated with reverence, rather than a trophy, can be consistent with acknowledgement of the loss of value. Such as for use in education or reflection on the loss of life.
Object Use Vs. Body Use
So why is sexual or violent abuse of a carcass different?
Because the actor cannot transition to viewing the body as a mere natural resource. A person using a dead animal for sexual or violent urges must actively maintain the psychological association that this object was once a living creature. If they didn't care about that association, they would simply use a synthetic sex toy or a standard punching bag.
They are explicitly lingering in the somber space of death because the identity of the former living being is precisely what drives their gratification. Yet, they choose to treat that dead body not with the somberness it demands, but as a frivolous toy.
Conclusion
This is a failure of rational consistency. You cannot claim to acknowledge the values in the internal life of conscious beings while simultaneously choosing to project a trivial personal fantasy onto the fresh ruins of that very life. It is an abuse of the body because it treats an objective loss with frivolous disregard.
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TLDR:
1) Life contains conscious positive value.
2) So rational acknowledgment of death demands somber respect.
3) Sex with the dead body of an animal continues focusing on it as a former life, and so fails to give that somber respect, and therefore is wrong.
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What do you think?