This is an interesting question, so I do want to respond sincerely to it. I really don't think that you can group male dogs and male humans together. First, as others have commented, we are capable of understanding that copulation can produce offspring. I don't care how smart the dog is, no male dog thinks, "Hmm, I want to have babies, so I think I'll meet up with that girl over there." Secondly, dogs are domesticated and completely dependent on us and our decisions. We didn't intentionally "design" them to need to be neutered to have a happy life, but we have brought them into a living situation where breeding often contributes to pet overpopulation. I was the one who decided to live in an area where there are many people and dogs (and possibly bitches in heat), so rather than 'encouraging' him to have urges that he doesn't understand, I decided to have a simple surgical procedure done that could potentially make his life less stressful. No agony over the bitch down the street, intact males are much less likely to bug him, and no chance of a "whoospie" breeding. Considering the overabundance of perfectly lovely pets languishing in shelters, that's just fine with me. Well, that's my reasoning, but of course everyone is entitled to his or her own opinion.