I guess you didn't know that dogs have some of the cleanest mouths--far cleaner than humans.
Dogs licking wounds can actually speed up the process of healing.
But otherwise, yeah, it's dumb to stick your face in front of an unfamiliar aggressive dog.
Look - if you let dogs lick your face, that's your business.
But to call a mouth that has just been licking dick, balls and ass 'clean', well, that's just nasty. I don't lick my own anus and my mouth is dirtier than a dogs that's just sucked himself off after some anal foreplay?
As for letting dogs lick your wounds, I hate to quote WIKI but....
"Wound licking is an instinctive response in humans and many other animals to an injury. Dogs, cats, rodents and primates all lick wounds.[1] The enzyme lysozyme is found in many tissues and is known to attack the cell walls of many gram-positive bacteria, aiding in defense against infection. Tears are also beneficial to wounds due to the lysozyme enzyme.
Wound licking can clean wounds and accelerate healing, so it can be thought of as a form of animal self-medication. There are a number of components of saliva that have been shown by scientific research to act against infection or to promote wound healing. In contrast to the benefits of wound licking,
there is also a risk of serious infection due to the introduction of oral bacteria and other disease organisms from the mouth into the wound, and animals may sometimes exacerbate wounds by excessively licking them"
Personally, as nice as it is that dogs have an enzyme in their mouths to aid in healing, the fact that they have shit on their tongues should put off any sane human from engaging in such bizarre practices.
Next we'll be hearing how clean cats are too. Cat's aren't clean either, they are just covered in cat spit.