IMO, no tech can make you offensive to others. How you use it, and your attitude, is what would make you offensive. If you go around "Do you have a smartwatch? *I* have a smartwatch!", then you're a jerk. If you just use it and show it off a little if people ask, then that's cool.
I will say that bluetooth headsets are more prone to coming across badly, because they give off an impression that you might not be fully listening to someone if you're wearing them while having an in-person conversation. IMO, bluetooth etiquette is that if you're talking to someone in person, take it out of your ear. Nothing like that really applies to a smartwatch, other than not letting it divide your attention too much from a conversation (same goes for a smartphone, tablet, or even a paper book).
What if I frequently hide my phone near friends, coworkers, or even strangers, step away several feet, then start ripping farts from my watch with the Whoopee Wear fart app? Does that make me a d0uche?