Carbohydrates are most certainly not 'unhealthy'. Care to cite any sources?
Umm, I think you did.
We in the US eat too much period. It's not about which macronutrient we overeat, though carbs tend to be easier to eat a lot of than fats or proteins, and are cheaper to create. But again, the focus needs to be on caloric intake, not on specific macronutrients.
It gets tricky in a few places: calories are labeled as the number of calories a food has in it, not the number of calories you net when you factor in the cost to the body of extracting those calories. 200 calories of chicken breasts costs your body more calories than 200 calories of sugar to extract. Especially if you don't end up using the protein to build muscle and convert it to energy. This isn't a massive difference, but it's significant. Regardless, calorie counting is about establishing a baseline and trending downward, not being 100% accurate in your calorie estimations.
As you mentioned, people with specific needs, like diabetics, are going to have different experiences with carbs, but that's a completely different discussion, and not one I know a ton about.
The body builders thing is interesting. I'm a power lifter and I lift with a lot of body builders so I am familiar. Insulin use like this can help the body absorb nutrients more quickly after a workout (specifically carbs, which can help restore glycogen to the muscles which helps with amino acid absorption) but it's not being used without an increase in overall calories (or it shouldn't be). In short, it's helping body builders eat more (especially post workout), not absorb the same amount differently. In my opinion it's a really stupid idea, though when you consider the trash many body builders put in their bodies it's probably less scary than a lot of the supplements and prohormones out there.
As someone who has used T, insulin is much more scary. At least with T it's been used for decades, we know how to mitigate the risks and handle side effects. You could easily kill yourself not knowing what you are doing with insulin, or probably make yourself diabetic. These oral prohormones are scary too mostly because of liver toxicity and because people could buy them without really knowing it (when they were/are sold at places like GNC).
Fats and proteins take longer to convert into glucose, and are less likely to cause a glucose spike and subsequent fat storage process.
Carbs are not unhealthy, especially if you can spend the energy immediately. However, it is very easy to consume a large amount of carbs in one go, thus a greater risk for an average person.
I am not nutritionist. I do know that after struggling for a decade of limiting calories and fat, I gave that up, limited myself too 100g carbs / 15g sugar a day, and lost 60 pounds within a year.
I still enjoyed Chipotle, but only the "bowl" variations of their food.
People fear dietary fat, but it turns out that fat is filling and actually difficult for the body to convert into energy, while carbs are the opposite.