I've never walked out of a movie in theaters, but that's only because I paid for the ticket. I think the most recent movie that I probably would've walked out of was the new Ghostbusters movie. I didn't even want to see that movie, I was dragged to it. I didn't hate it because it was gender bent, either. I hated it because it was bad. It was so bad that at one point during the movie, I left the theater room, went into the handicap bathroom across the hall, and screamed in frustration. TWICE. I only returned to the theater because I paid for the ticket. (By the way, somehow that movie got a Certified Fresh rating on Rotten Tomatoes. I now only take Rotten Tomatoes ratings with a grain of salt.)
However, I usually rent movies more often than going to the theater (pro tip: if you rent movies from the library, it's free!), and if the movie sucks, I usually just stop watching the movie and return it. For example, a few weeks ago I decided to rent '2001: A Space Odyssey', mainly because it's supposed to be a really good movie. Remind me never to watch a Stanley Kubrick movie again. Absolutely nothing in the film is explained to you. I couldn't even enjoy the movie because I was too busy trying to figure out what the f*ck was going on at any given moment. about 2/3 of the way through, I just gave up and stopped paying attention.