I don't think they have a case, and I agree with the above poster who said 15minutes isnt enough time to get horses up and get to a doctor...that scenario would have been more believable if say they had contacted you either late that day or the next day...
THAT ALL BEING SAID... having lived in a state where the farmers think they own the road especially during harvest season (NEBRASKA).....Im assuming by country road, you mean gravel.. IME 35mpg on a gravel road is NOT courteous. Especially when hauling clacking equipment...if you can see any sort of dust, you are not going slow enough. Flying gravel has a way of unnerving even some pretty traffic seasoned horses.. ( I might add this only applies to gravel)
I pay my county taxes just like everyone else, so sorry but it doesnt matter if im on a horse. I still expect some decency towards the fact that im on a flighty animal.
When I realized the farmers werent going to slow down for me even after complaining, I started riding in the middle if the road so they had NO CHOICE but to slow down..pissed em off but if they are going to be rude, Ill be rude right back.