We're pretty off track given that ya'll are nitpicking the metaphor rather than the actual topic, but claiming that horses were never common doesn't really have any connection to the claim that per-mile-moved / per-human-carried, horses are also dangerous.
Never use analogies when arguing online. It only ever results in exactly this, people nitpicking the metaphor. You've essentially given them a way to "be correct", about something irrelevant.
