All the dog shit collectors here: you don't pick up every poop if you let your dog off the lead, ever. So someone might bump into it.
There are more dogs in this mad country, than cats. EVERY fucking dog shits outside. SOME, if not most cats, have a litter tray at home which they use. There are no indoor dogs, but a lot of cats are indoor ones (pedigree, sick ones, or those in flats). So I dare suggest the amount of pet shit outside is skewed towards dogs, not cats.
Not everyone has a garden - let me remind this to some of you who probably forgot about people living in blocks of flats, cramped into hideous urban people kennels, because you tend to live in some wisteria clan village cottages - where they can encounter cat shit. EVERYONE walks on a road and sees dog crap there. Every fucking one encounters it at least once in their lifetime.
Not every garden is covered in cat shit. Mine isn't, my neighbours aren't. Everyone where I live is friendly towards cats.
Dog is a pet either pathologically incapable of shitting at home, like a cat, or it never crosses the mind of their entitled owners to train it to use a litter tray. Well of course, how could you? It's a dog abuse!
So, dog shit is universal and everpresent. Cat shit is localised to some unfortunate gardens. I am sorry it happens to people, if my cats went outside, I'd offer some solution to the distressed neighbour, but please reign in your cat-hate. Use your brain, think critically and see that, given who spreads most shit, the dogs are most offenders yet they are entitled to crap in public places and don't get so much bashing as cats do. So your cat-hate is unfair, like any stupid, bigoted prejudice.
Neighbour vs neighbour is, like everything, a matter of manners and communication skills. People often lack it and express their indignation in an obnoxious way which invites a similar response. Either way, when politely told of the problem, a good person would apologise. That this doesn't happen is probably another half of the problem. That, or far too many cat haters on earth, sadly.
Every pet shits. It's unpleasant but not the end of the world, and cats are no worse than dogs.