As for horse muck there are, unlike with dogs, no harmful chemicals that pass through a horse, so use it on your garden!
As for poop bags on horses of any kind, this is utter rubbish.
When you see them on TV, such as horses on royal parades, there is was poop all over the place.
Yes, I am horse owner and have heard this subject time and time again.
Yes, I do ride my horse out but never on pavements.
In 20 years I have had to go on pavements twice when young, just to let thing go past then we’re straight back on the road.
I’ve been a horse owner for over 40 years and we are approachable - if you see one doing it, then ask the rider to politely clear it up if and when they can do so.
Horses have been on roads longer than cars and will be here for long time
Don’t forget horse owners get more abuse than anything -we all go to work and work hard for our hobby they not cheap to keep.
Let people have free manure, what more do you want?