I once had my horse at a barn for a summer where the owner did things like ask me why I didn't lead my horse around with a stud chain over her nose. Huh? My horse has near perfect ground manners, which I pointed out, and crazy BO said that if something scared the horse and she jumped forward, then what would the mere halter do to stop her (and a chain wouldn't scare her or anything, right).
The worst thing she did though, was I when went away visiting the parents in another state for two weeks. I phoned the BO at one point, just to ask how Gypsum was getting on. I'd asked the BO to ride Gypsum while I was gone. In spite of her weird ideas, as illustrated above, she was an okay rider. Had some odd ideas in that department as well, but at least they were fairly harmless ones in the case of a schoolmaster like Gypsum, i.e. a horse shouldn't be worked in collection or even on contact for more than 15 minutes, ever. Fine, whatever, so she gets to faff about on a long rein for two weeks. Big deal. Anyway when I rang her the BO replied that she'd called the vet and had the vet do a blood test for EPM*. What? She said that Gypsum was stiff to the right (like what horse isn't) and that was a sign of early EPM. I observed that most horses are stiff to one side or another and her response was that a lot more horses have EPM than are diagnosed. What about horses in the Western US or UK where they don't even *have* EPM (I have told this story to UK friends and they are like, "what is that?")? Her response is that EPM obviously exists in these places but people don't know about it yet. I had also vaccinated the horse against EPM before I'd moved her from Colorado to the East Coast. Obviously crazy didn't know this, nor did the vet, as no one bothered to tell me they were sticking needles into my horse until after the fact.
Needless to say, the results came back very very low positive, as you would expect if you'd been vaccinated for something. I told the vet about the vaccinations when they phoned me with the results. "Oh, we were unaware of that when we drew the blood from your horse." No duh -- cause no one told me you *were* drawing blood from my horse, you eedjits. And I had to foot the $150 vet bill. Was not impressed.
*Blood tests for this are somewhat vague and inconclusive. To diagnose it properly you need to do a spinal tap, which is a far more invasive procedure.