Oh I see!
It’s ok to make a negative judgement about a diverse lot of people based on the fact that they own one type of animal?
Do you know how ridiculous that sounds?
Do you think all hamster owners might be paranoid for example?
Maybe all parrot owners are prone to jealousy?
Or perhaps owners of ferrets are particularly hospitable?
Leaving that aside, the reasons that horse riders are allowed to leave “piles of crap in their wake” as you put it, is nothing whatsoever to do with morals, ethics or courtesy. The reasons are entirely factual and practical:
~horses can’t be trained to poo on command and therefore they poo at liberty, sometimes while being ridden on roads and their owners do not have any control over this whatsoever
~it’s entirely impractical for them to get off in the middle of a road and clear it up because it’s not terribly easy to hold the reins while also holding a bucket and shovel and also it could be dangerous to other traffic users to cause a hold up
~if it were possible for us to clear it up, where do you suggest we park our horse while shovelling?
~if there was anything about it that was dangerous or toxic then we would be required by law to pick it up and there isn’t.