Sorry, but that doesn't make any sense. If the risk is insignificant then of course the owner should tolerate it. All the stuff about STIs is transparently just a post-hoc rationalization of people's disapproval of prostitution.
So... time to rethink your position; I'd be absolutely furious in this guy's position, and "The risk is incredibly low," would frankly piss me off even more. Your argument is about as weak as someone smoking a ton of pot in someone's house, then bitching about prohibition. I'm against prohibition, and also against you stinking up my house.
If you try to pigeonhole all of the people you disagree with, you will turn into a caricature no less absurd than the ones you're trying to create.
Plenty of people who think that prostitution should be legal still disapprove of it, by the way.