A movie theater or restaurant is not comparable to an aircraft.

For starters, you can't just leave a plane in mid-flight.

A crying infant in a movie prevents others from hearing the movie, but in a plane, they don't prevent anyone from getting to their destination.

There's little point in even bringing infants to the movies, but they must fly to reach certain destinations.

Restaurants are a bit of a gray area, depending on cuisine, etc.

The elitist part comes in with the attitude that somehow 1st class passengers should be spared the crying baby while coach passengers should not.