Neutered male dogs are much more contented. The constant urge to mate, roam, mark and compete can be very stressful for a dog.
It is usually blokes who object on the grounds that they wouldn’t like it doing to themselves. Don’t anthropomorphise, it isn’t the same thing – the dog is completely unaware and will lead a healthier, happier life. This isn’t a personal opinion, it is well researched and I’m sure any vet/animal welfare person you spoke to would say the same.
With the amount of strays and unwanted dogs in shelters, it is the responsibility of any animal loving person to spay and neuter their dogs.