Ahh, the old "neuter" debate .. *L*
As a vet tech, I saw numerous cases of testicular tumors. Maybe those unneutered dogs in orion's country died before anyone noticed testicular tumors. Who knows? But the reality is that there ARE a lot of testicular tumors and the only one to blame when a dog ends up with that is the owner who didn't get their dog neutered.
Another health problem seen in intact male dogs is prostate enlargement and subsequent urinary problems. First sign is generally that the owner notices the dog is urinating blood. An intact male often has a prostate enlarge because he smells a bitch in heat and is aroused. Why put your dogs in this position, where they are feeling the effects of hormones that they're not allowed to use?
As far as behavioral issues go .. established behaviors may not change with castration. But a dog that is castrated before it learns to roam and search for a mate, or mark his territory in the house, will generally not learn those after neutering. Behaviors that are hormonally based will not happen as the source of the hormones has been removed.
And anyone worrying about what his dog might think about losing their testicles is projecting WAY too many of their own feelings on the dog! *LOL* One of the reasons dogs bounce back so quickly after most surgeries is that they don't put the emotional attachment on things as we humans do. A bitch with a mammary tumor removed isn't going to mourn the loss of her breast. A dog with an amputated leg is not going to mourn the loss of the leg - they won't think back on how they can't do the same things they used to do. They just adapt and go on, which is a survival technique.
Males don't "miss" their testicles, nor do females miss their ovaries and uterus after surgery. They deal with the discomfort at the time, and life goes on.
Reminds me of the old joke where the woman had one wish, and wished that her dog would be a handsome man. POOF! it happened .. and the man turned to the woman and said "don't you wish now that you hadn't had me neutered??"
It's all wishful thinking to believe that dogs worry about losing testicles or any other part.
Melanie and the gang in Alaska