I wouldn't want to wish such an accident on anyone, but horseriding is one of the most dangerous sporting pursuits. It would be interesting to look at just how many accidents/deaths there are to horse riders each year. I have experienced several instances of nervous horses nearly throwing riders adjacent to busy roads, where cars are passing within a few feet of horse and rider and you don't see measures being brought in to prohibit cars or horses from roads to prevent accidents. I'm not sure there's a definitive answer, but they do seem to have over-reacted to me.
2Sticks