How do you say Hello in dog?

I bring our dog, Yawkey, into the office with me several times a week. The past couple of weeks there has been another little dog here named Tucker. These two are totally gay for each other. Keep in mind, I am cool with that, you do your thing. This, however is just plain wrong. They are constantly licking each others private regions, trying to hump one another in the face, and all sorts of ass sniffing. Now, this seems fairly normal for dogs, at least when they are younger. My question is this, could I get away with that? If someone new entered the room and I shoved my head into their ass and took a big sniff, would that be acceptable? If we had a couple over to the house for dinner on a Saturday night, would me dry humping one of their legs be cool? I'm guessing not. But why? Why can man's best friend get away with it, but not man? I think from now on my introduction to people will be a quick lick on the neck followed by a nose in their ass. It's cute when a puppy does it, should be when I do it, I'm just saying...