The thing was so controversial in the US that there were segments about it on nationally broadcast news programs like Good Morning America or (maybe it was Today), and the one I saw featured a panel of 8 professional adult taste testers. What makes them professional is that their training is to be able to describe a food without using preferential adjectives like, "this tastes great" - they have to use specific adjectives that relate to spices or specific flavors/textures.
After the professional review, they were asked what they personally thought about the double down, and most of them said they'd eat it again, though they all seemed to express they wouldn't actually plan to eat it again. Just that they would because it tasted good overall. Most normal adults don't "plan" to eat something extremely high in fat, cholesterol, salt, glutamates, etc.
edit: in response to neo duality's comment comparing it to a cigarette,
if you plan to smoke just one cigarette, and do it, and don't go back.
then you eat just one double down, and do it, and don't do it again,
the damage done by the sandwich is arguably worse than a single cigarette, even if it's an unfiltered rollie.