I've been interneting for too long for the thought to disgust me. I mean, don't get me wrong, it's not something I fancy, but I don't automatically react with the feeling that is disgust.
I remember reading about a human playing sexually with a dolphin and it seemed they both had fun
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Have you ruined me internet.
I guess some of the question would be how ok it is to do something to someone/ thing who are ignorant and unable to map out a wider array of consequences.
Like would it be ok to have sexual contact with children if it wasn't done forcibly, but in a safe way?
(Though, considering the taboo and attitudes around it, it wouldn't be unlikely the person grows some sort of mental conflicts/ issues when becoming an adult and realizing what happened).
Would it be ok to have sexual contact with a toddler who wouldn't remember it as an adult?
Would it be ok to have sexual contact with someone in a coma?
(A chance they'd find out, though)
With someone with mental retardation where one can practically make the low intelligent individual partake in most fetishes as it's less capable of knowing what's good for it in the long run.
These questions are similar in nature.
Animals don't have the mental capacity to understand complex behavior and understand what might be harmful them in the long term. I guess when it comes down to it, I see the reasons against bestiality to be similar to those against sexual contact with children.
I don't think most would have a good enough understanding of animal nature and ability to read subtle clues in a way that wouldn't lead to a net suffering for animals overall.
So here is my answer, if you'll indulge my disgustingly circular logic: Disgust is a moral emotion. It is a universal reaction to a violation of something one holds as sacred. Most people hold sex as sacred in some way. So, since most people have a disgust reaction at the thought, then disgust, in itself, is a moral reason not to fuck animals.
I don't know, it seems too shaky a ground for me. I mean, sometimes we're disgusted by the weirdest things (like brown spots on bananas, eww), sometimes the disgust is very culturally inclined and sometimes we've seen disgust for a thing disappeared as we advanced through ages.