Yeah...but in context, "gullible" seem a bit pejorative. Humans are also hopelessly incapable of sensing radioactivity, methanol in their alcoholic drinks, carbon monoxide, and a great many other things that our ancestors just didn't encounter much.

Though we're pretty good at sizing up a person's emotional balance/maturity and competence at familiar tasks. So maybe have an old blacksmith watch the AI/robot interact with horse owners for a while, then shoe their horses, and see how well it does.