Q. See original question above. (Can I eat popcorn in a theater if all the ingredients are kosher? Is it not proper for one to eat in a public place?)
A. Horav Shlomo Miller’s Shlit’a opinion is that since you are after all seating in a theater, (assuming that there is a proper Mechitza between men and women and the presentation is also proper), since people usually as in your case benefit from the kosher food available, there is no issue of the avoidance of not eating in public, being similar to a wedding or other permitted seudah.
Rabbi A. Bartfeld as revised by, Horav Dovid Pam, Horav Aharon Miller, Horav Chanoch Ehrentreu and Horav Kalman Ochs Shlit'a