Here's a better analogy:
Amazon sells set-top boxes. Apple TVs, Rokus, the works. They also sell HDMI sticks, like Chromecasts.
All of a sudden, they come out with a product called the "Fire TV". It integrates with Prime, and in comes in either stick or box form, depending on your preference.
All is well in the world.
But then, all of a sudden, Apple and Netflix and Google find that their Amazon product pages for Apple TV and Roku and Chromecast (respectively) aren't published anymore. When they ask Amazon about it, Amazon stubbornly replies with some rule in their ToS about mentioning competing products.
Is Amazon's behavior in this scenario ethical? Is it worthy of brushing off as "that's how the market works"?
This differs from your analogy by the order of events. In your analogy, your movie theater existed before the attempt to buy an ad for a competitor.
In the case of my analogy (and, indeed, in the case of what Apple's doing now), it would instead be akin to you running a TV station that runs ads for a theater, you opening up a theater of your own, and you then banning the ads of the other theater while running your own ads on the TV station you own.