You're wrong and right, but I know you won't argue cause you said you wont.
The time has no effect, nor does not getting a baby sitter since at 3 months, it's likely the baby is still wanting to nurse entirely sporadically and may be every hour or ever 2 or 3, so it's better to bring the baby with you wherever you go. Time... well babies don't sleep 8 hours straight, the go an hour or two and then need to be fed, and it's likely the baby sleeps better in the moms arms anyway.
Should a parent with a new born go to a theater? The only reason not to is 1) it can damage the hearing if too loud, but they make baby ear muffs so this can be easily rectified. 2) the other patrons.
My guess is that the mom was probably sitting right next to the exit which is probably why she/the baby was shot.