In other words, you're more likely to catch a cold from shaking their hand than to get an STI from Sitting on the same bench.
There isn't much reason to fear getting a sexually transmitted disease from naked sitters. These infections are most commonly the result of vigorous and prolonged exposure of a person's mucous membranes, the thinner and more permeable skin found in the mouth and on the genitals. If you happened to share a seat with an infected nudist, you'd be protected both by your clothes and by your epidermis, which serves as an effective barrier against pathogens all by itself.
There are a few things I like about this story:
1) Not parroting a politician's views, but actually fact-checking them. 2) Pretty good reporting on the science, complete opposite of fear mongering 3) I learned that San Francisco doesn't ban public nudity
Way to go Slate!