Speaking from experience, learning how to stop crushing your junk while horse riding is something that happens extremely quickly. Especially if you have a girlfriend who will provide additional junk crushing if you give up on horse riding too soon :)

Said girlfriend worked on a horse riding yard in the UK. Most of the instructors were female. One of the few male instructors, at one point, was managing to *ahem* court four of the female instructors at the same time. He'd been riding horses for over a decade, so I must assume he figured out how to protect his essentials.