Not sure if that distinction holds up. It seems to me that the adjective "stupid" is generally used for people or their actions where the displayed lack of intelligence cannot be justified by an innate lack of abilities. I.e. one would probably not refer to a mentally handicapped person as stupid (not nowadays anyway). Personally I would never refer to a person who lacks what you call critical thinking skills as intelligent even if they are well educated.
Jamie, here's the dictionary definition:
stu·pid [stoo-pid, styoo‐] Show IPA
adjective, stu·pid·er, stu·pid·est.
1. lacking ordinary quickness and keenness of mind; dull.
2. characterized by or proceeding from mental dullness; foolish; senseless: a stupid question.
3. tediously dull, especially due to lack of meaning or sense; inane; pointless: a stupid party.
tunalegs' comment was spot-on: "Unfortunately a lot of people are taught to learn - rather than to think."
We regularly see very intelligent people making huge mistakes by failing to think critically. The first that comes to mind are professionals who join a cult, but I'm sure we could come up with a lot more examples really easily.
But to get back on topic, the point I'm trying to make is that it's not so much about being 'sucked in' by peer pressure, it's more about weighing one's interest. Obviously I'm not talking about severe cases like anorexia, bulemia or teenagers using steroids where one could talk about them succumbing to peer pressure, I'm talking about most of us who consciously decide to do one thing or another based on societal pressures.
It is interesting that this very thread has turned into an exercise in critical thinking! Disordered eating is almost completely misunderstood by the public. People don't
choose to have eating disorders. They
choose to lose a few pounds or work out... and in some cases that can trigger the beginning of an eating disorder in people with a specific personality type. At least with anorexia, there seems to be a type of personality that is more prone to developing it. An eating disorder is triggered (at least in anorexics) by some as-yet-not-understood bio-chemical reaction that not only shuts down the desire to eat, but actually makes food seem toxic. It's not a willful act; they actutally
can't eat. There's a variety of other symptoms that occur as well. But it seems that one of the common triggers is rapid weight loss; sometimes as little as five pounds in just a few days.
Where the advertising/peer pressure/unhealthy and impossible body image issues come in is when a person feels the need "to lose five pounds" to meet a body image goal so they can be viewed as more attractive/interesting/whatever. That's not a trigger in all cases of course, but anything that encourages rapid and unhealthy weight loss in an otherwise healthy person can be, and that's why these ubiquitous un-attainable "ideals" need to be changed.
Now, that certainly doesn't explain anorexia in a nine year old, of course... and frankly from my research, most facets of eating disorders are as poorly understood today as the plague was in the middle ages. Modern medicine is still largely in the "bloodletting and leaches" stage of treatment in most cases when it comes to eating disorders. While eating disorders appear to have mental health symptoms, it is more likely to be a chemical/neurological disorder, not a mental disorder. Modern eating disorder treatment in most cases is barbaric, and just doesn't work. Fortunately there's research being done, however minimal at the moment.