STPs tend to like pushing people's buttons. They don't automatically go for pissing you off though, though some do.
Most just enjoy getting a reaction out of people, and that includes emotions such as giddiness, awkwardness, snarkiness, competitiveness, etc etc. I just spent the entire day with my ISTP boss today and we did nothing but exchange verbal jabs and comments, something he *always* starts coz he somehow enjoys my reaction to what he does. It unnerved me at first, and sometimes still does, but it's also tons of fun