I think in general it’s considered rude to mention that someone is stupid, unattractive, poor, etc. Overall, people are already suffering from low confidence due to these issues and pointing them out only hurts them. Unless someone is seeking out honest feedback in these areas, it’s probably better not to volunteer any. On the other hand, it’s fine to talk about how society has a problem with education, poverty, or obesity and suggest society-scale solutions.

Agreed... a few years ago, I was getting a bit plump in the mid-section. My wife's grandmother from Colombia strait up told me I was looking "gordo" (fat). I got on it immediately and shed the spare tire. I thanked her for being honest and open... I wish I could tell others the same.

“Choose not to be harmed—and you won’t feel harmed. Don’t feel harmed—and you haven’t been.” ~ Marcus Aurelius