They never said it’s the only way they can control their calorie intake, they said that a reasonable meal from there is less calories than most meals they cook themselves. Very clear cut statement. Don’t put words in their mouth.

Artificial sweetener is possibly dangerous in extreme quantities (several gallons of diet coke every day), but even that doesn’t have the strongest scientific support, it needs more research. Processed foods have had similar amounts of proof that they are possibly bad for you, possibly. In large quantities. I don’t know if you noticed but they never said they eat McDonalds regularly, or even often, so that is another assumption you made that they have a “McDonalds centric diet”