I could imagine them taking a patriotic tack and inviting everybody to show up well armed to the showings. Or heck, put it up for streaming at $15 on all the major providers, let the terrorists hit every data center between here and Pyongyang.
I've never seen an instance where armed law abiding citizens made a terrorist attack or mass shooting worse. If you know of any, I'd love to hear about them.
I cannot. I can name numerous situations where one "armed law abiding citizen" has shot another "armed law abiding citizen." If people came armed to a movie, I wouldn't go, not because I fear a "terrorist" attack, but because I fear armed individuals in general.
And statistics back me up, the number of people in the US killed in terrorist attacks is insignificant relative to the deaths from gun violence.