I find it fascinating how people seem to expect dogs to put up with almost anything humans can throw at them, and the second they lash out in self defense (invariably after giving plenty of warning signals) there's calls for them to be put down. When a horse - which can kill a human with far less effort - lashes out in self defence there seems to be much more understanding. I'm not sure why there's such a huge variation in tolerance.
For me, there's no difference between a horse or a dog reacting to a perceived or actual threat/pain and, they're both animals with limited reasoning skills, no matter how good at training you are, you can't change that.
The difference for me is that horses are prey animals and dogs predators, therefore dogs are more likely to be aggressive than horses, but by their sheer size, horses in self defense can cause more damage with little or even no intention. I've had broken bones in my foot from a horse who had flies buzzing around his front legs, maybe a horse fly taking a chunk out of him, and he stamped the foot to move them. Zero intention to hurt me, I didn't scare or startle him and nor did anything else, but by his size and power, I was hurt. It's a perfectly reasonable thing for a horse to do to prevent himself being bitten by a fly. The responsibility was mine, and I should have kept my feet out of the way!
Had a dog done that, well it might have smarted but I doubt there'd have been any damage.
I think the issue with dogs is maybe that they are perceived as aggressive when actually, they've been defensive and the person on the other side has failed to read the warning signs - for whatever reason.
The real problem though, is not people not knowing the warning signs, it's attempting to approach and interact with animals that they have no knowledge of. Owners have a duty to keep their animals under enough control that they don't interact with people uninvited, and others have a duty to not interact unsolicited unless permission is sought and they are aware of the danger that could be present.
Unfortunately, neither side can be guaranteed to uphold their side of the bargain, because that's human nature.
I'd personally advocate more tolerance and understanding of dogs, rather than less for horses, before anyone has a go.
I'd absolutely advocate that too, for all animals, we seem to forget that they are animals, we humanise them and attribute skills to them that we think they should have, but don't. Or think that owners can instill these attributes through training, a certain amount certainly can be, with most animals, but their primary instincts will always be to protect themselves, and their food source primarily.
Incidentally, I find cats more tolerated and defended than either horses or dogs, when they follow their natural instinct to roam and hunt.