Really bad reason to use deadly force. I can understand folks getting irritated about talking during a movie, but texting?? This has the potential to give lawful CC a bad name.
I am for constitutional Carry, and would actually update the state DL database with those who are prohibited persons (everyone else is permitted), but I would also encourage everyone to take an annual class (1 day legal, 1 day training) and do it at state expense. There is a massive public safety benefit to having a well-trained and knowledgeable population.
I agree the overreaction seems clear, but texting in some was worse than talking because the phone screen is distracting for a longer/wider area.