I am curious. When you're out in public and see a hot girl, do you go like "Man, wish she puked on me" or "Would love to see that babe munching on my turd!"
Nope, but that's because it's not my kink. I will find myself imagining said girl in a scenario that turns ME on, as do you.
As long as the proper precautions are taken, and all adults involved are consenting, who is it hurting? Why are you so concerned with what others do in the privacy of their bedroom/kitchen/shower/vomitorium?

