No, read it again. Trademark disputes are not about customers being stupid. They are about protecting company assets, in this case an intangible asset which has economic value. As for Pizza Hut suing over that slogan - if they trademarked that exact phrase, it's theirs. That's why we register trademarks. You can't sue over a trademark you don't have, but you can when you've been awarded the right to tie a name or slogan to a company. Pepsi-Cola is not the same as Coca-Cola, as the trademark office determined when they let both be trademarked. Has double cheeseburger been trademarked by McDonald's? Doubtful. The trademark and patents office doesn't allow trademarks on everything.

My closing comment?  Was in response to the poster who said customers aren't stupid, which I gave a reason for doubting.  But it doesn't mean that trademark disputes are about customers being stupid. They are about protecting names and phrases the government said they can protect and gave them rights to do so.