Well I am the carb police 
LondonMan
"I seem to recall being taught in primary school that "carbs" were what humans were supposed to mostly live on. (i.e. that rice, potatoes, wheat etc. were staple foods.) Obviously there is a difference between those and high-fructose corn syrup."
Carbs are not what humans were made to live on. When we first roamed this earth, we relied on what we could hunt to eat - so mainly meat/fish, supplemented by whatever fruits/veg we could find in season.
"I think the bad reputation of "carbs" is a fad. I believe the reason low-carb diets work is that they make you eat more meat. Apparently eating meat kills appetite quicker, resulting in fewer total calories consumed."
It isn't a fad. There is a huge body of evidence to support the fact that carbohydrate causes many of our Western diseases, including diabetes, hypertension, heart disease, cancer and Alzheimer's. Low carb diets work because they control your blood sugar levels, and in particular your insulin levels - so your body lays down less fat. The fact that you eat more fat and protein means your appetite is also satiated more easily. A low carb diet is not a low calorie diet, in part because of the amount of fat that you eat.
And, before you all howl in protest, there is actually no proof that fat causes heart disease.