He's actually very horse-smart. He just doesn't think chopping off a horses nuts is fair when he didn't do anything wrong. It's not the horse's fault that he had bad breeding or faulty trainers. I see what he means, but fair or not, its something that needs to be done.
Odds are you, your boyfriend, and the horse will be far happier if his family jewels are gone. Regardless of your boyfriends "personal" feelings that simply are his relation to having his own jewels and rather not be neutered. When in truth, there is absolutely NO comparison to the two and shouldn't be compared, imo.
My mini colt only dropped one testicle which means (as I told my hubby) the vets will have to "dig/cut" the other one out once we find where the bugger is hiding, that alone sends his knees to pinch and cringe. So I can sympathize your boyfriends ignorant view on the stallions jewels.
Simply not gelding a stallion for remorseful reasons is all the more reason to geld them. If you don't have the facility to own one, you don't need one. There are plenty of studs out there, don't let him keep his jewels, especially if he has no redeeming qualities of a stallion, just because your boyfriend (or you) "feel bad" for gelding him. :P You'll thank yourself later :)
I always heard that "A good stallion will make an even better gelding." My mini colt would be a cute producer (of color) but his sickle hock, overbite, awkward looks, argue "Pretty" over "Functionality" thus he's being gelded
Although I do sympathize with you. A friend of mine refused to neuter his dog because "I won't do something to my dog that I wouldn't do to my kid." Apples to Oranges