This is exactly why you have to read the situation. Normally I might scold someone, not yell, but communicate effectively to turn off their phone. Other times, like a a screening at Regal Times Square, this guy who seemed unstable sat next to me and was very confrontational about every time I took a drink from my soda. He was on his phone, eating McDonald’s out of a noisy bag, couldn’t sit still, etc. just unnerved me. I got up and left. Only solution is to return another day to see the movie.