I bought an open stock four-horse bumper pull trailer brand new in 1987. It is 6'6" in height.
The front has a removeable divider, the back is completely open for two horses to stand side-by-side
Besides hauling all over OH and PA trail riding, when I moved, I hauled three of my horses from PA to SoCal in that trailer. Five years later, I hauled those same three horses to Tennessee.
I still have that trailer and those three horses who went to many trail rides, parades, and cross-country twice. Nobody ever got so much as a nick of the skin riding that trailer.
While nobody has ever said anything, I have received some condescending-down-their-noses-looks for carrying my horses in such a low-life/no class trailer but, guess what? It still doesn't have any serious rust on it, the frame is solid and best of all it's been paid off since 1990
Sounds like you're dealing with the same no-class type of folks; I guess some things in the horse world never change
Further to Cherie's comment, back in the 60's my ex-SIL's uncle loaded one of his young QH's in the bed of his truck and hauled it from OK to OH as a 14th B-day surprise for her. Horse had never been anywhere, he put the racks on the truck, said "get up in there" and away they went. That's how my grandad also used to haul horses and nobody got hurt. BUT there was a lot less traffic back then, even going state-to-state; I wouldn't do that in today's whacko world.