Imagine, if you will, going to a new film, one you have been anticipating for a few weeks and are excited about seeing. It's turning out well, the story is well written, the cinematography is top notch, and the actors have put in the performance of their lives. Then, in a key moment during the climax, you notice a distinct chirp and a blinding light in the distance. Someone has decided that this is the perfect moment to start texting someone, because they're horrible people, and all you can see is the bright beacon of annoyance that a cell phone in a darkened theatre represents.
I'm not someone who thinks a theatre should be a silent tomb. Genuine reactions are expected and can enhance the experience. A comedy without laughter is just depressing, and there are many moments where an audience reaction can improve the experience. The most memorable part of Titanic for myself was a kid asking if the ship would make it to land very loudly, and that unique memory has long since eclipsed the rest of that film. Conversations among theatre patrons can be annoying, certainly, but sometimes they're amusing, provided they're on the content on screen. It's a trade-off inherent in any such communal experience, and for the most part other distractions can be ignored.
On the other hand, I don't object to texting in other situations. At sporting events, I'll sometimes text the score to friends who aren't around. It's perfectly fine in situations where the ambient light makes the phone not noticeable, and the ringer is set to either off, or my own phone's special setting of technically on, but will never sound the alert. The reason is that it's not distracting, since you can't see it.
That's why texting in a theatre is a mortal sin. See, phones are very bright. I have used my phone as a flashlight - admittedly, in order to find a better flashlight, don't ask - and as a result a powered up phone can be seen from any corner of the theatre. It's the same deal with music performances or any situation where you're in the dark, and other people might want to see the thing on stage or screen, rather than some idiot talking to their friends.
While I can appreciate audience reactions to things happening, with text that's not the case. The person on the other end might be doing their laundry, or they might even be going into labor or chased by an axe murderer, but they're not watching the film. There's no genuine reaction here, just an unrelated conversation. This is fine, provided I can't see your conversation. However, in a darkened theatre, I can, and that drives me completely insane.
Recently, a theatre got an angry message from a patron who was kicked out for texting during the movie. My reaction is more theatres should do the same, maybe figure out how to block reception during show time. If they can't watch the movie, at least allow me to watch without distraction.
It's hard enough to convince people to go out to see a new film. Home televisions are getting larger all the time, and improvements in technology mean movies look better and are easier to access than ever before. When other patrons decide to ruin the experience by fiddling with their ridiculous phone during the show, I can't help but wonder why I bother to go in the first place.