As long as the horse wasn’t drunk, I don’t see a problem with it. In great-grandfather’s day, it was common to give the horse control to bring both horse and rider safely home in a storm. The horse was smart enough to do it by feel when the rider couldn’t see.
There’s some logic to that. I’ve occasionally wondered about the fairness of public intoxication charges. Presumably professional sports venues or concerts aren’t public places, because there are many intoxicated individuals. I suspect this guys problem was riding down the middle of the road. His defense attorney can blame that on the horse.