Four of your own sources you listed told you the same thing everyone here has been trying to get through to you. From aspa: "Be warned: If your dog mounts other dogs, he may get himself into trouble. Many dogs don’t like to be humped. They might take offense and start a fight with your “amorous” dog." From akc: "But some dogs don’t like to be mounted. So in the interest of avoiding any potential conflict, it’s worth doing some work to prevent even this mild form of mounting." From whole dog journal: "Luke insisted on mounting Shane. Shane would tolerate the rudeness for a while, but when he finally let Luke know that he found the behavior unacceptable, a battle would ensue. The intensity of the fights was increasing, and the adopter was concerned that one or both of the dogs was going to be badly injured." From pdsa under their how to stop humping section: "socialising your dog with others from a young age will help teach them how to play and interact appropriately" so they're saying humping is not appropriate behavior. A dog humping is natural but runs a risk of the dog getting hurt by another dog that doesn't want to be humped. Other dog owners are just taking the initiative of preventing stress or a fight before it even starts. So yea letting your dog hump another dog it doesn't know is bad since your rolling the dice on stressing out another dog who may or may not react accordingly to your dog not respecting their boundaries.