But that doesn't mean the courts will side with me and not you. Strict logical coherence isn't always adhered to. It's even been called "the hobgoblin of little minds" - so perhaps Emerson would take your side on this.
You don't make the mattresses yourselves, you purchase from a manufacturer and sell in your storefront. There are only a few different mattress manufacturers.
Your rival, instead of adjusting prices or organizing better marketing, simply plays the manufacturers not to sell to your store for six months.
Unless you can rapidly find a brand new source of mattresses or have a very healthy rainy day fund, you will likely go under fairly quickly after selling your remaining stock.
This leaves only one store in town, and they can set the price to whatever they want. Now that they are the only established incumbent they can easily recreate this scenario with any new mattress stores that want to open in your city.
Now the people of your city have only one store for mattresses, and have to pay whatever is asked for. This is not because the business did anything especially well to win more customers, or because you did anything wrong. They simply destroyed the competition through anti-competitive behavior and have negatively affected everyone else in your area.
This is why it is illegal.
As well, although this may not contradict what you intended to say: patents, for example, precisely grant "the right to exclude." Exclusive territories are a frequent way to do this. So in that case, it isn't necessarily illegal.
With console video games, you can’t just pop the game disc into any disc tray that plays games. You can’t run your downloaded Xbox game on the PlayStation. The thing you licensed (since we don’t own them technically) is tied to proprietary hardware.
Imagine if you had to own a Mac in order to listen to your music you bought on iTunes/Apple Music
[1] https://support.microsoft.com/en-us/topic/support-for-rights...
Imagine if any music I buy on bandcamp could only be played via a bandcamp app or software on bandcamp’s proprietary hardware.
Sure, its great for 'consumers', but it won't be long term. Will Xbox require mandatory three year game pass or onstar when you buy it? Would that be an antitrust violation?
As you point out, it's pretty accepted in the copyright industry to have exclusivity deals. If I want to get Katy Perry's album, then I buy the Capitol records one, I can't get it from Sony. Or I can only stream on services where that artist is available, so if it's not on Tidal, then tough luck for users of that service.