I was out drinking one night many years ago right around the time mullet spotting became a meme. Several beers into the evening I spotted a college age kid walking into the bar sporting a classic example of the tennis mullet. Being a service minded individual (not to mention very drunk) I marched over to him and asked him if he was aware he had a mullet and directed him to http://www.mulletsgalore.com/ the next time he was near a computer. The kid looked at me like I was nuts but he wrote the URL down. Mission accomplished I went back to drinking with friends.
A month later at the same bar I was approached by a vaguely familiar dude with a sharp looking haircut. He introduced himself, thanked me profusely for telling him about mullets and bought me a round before joining up with the rest of his friends. Apparently the kid just hadn't heard of mullets yet and I'd done him a real service by bringing him up to speed on the subject.
Classic! You might have done him a service, but perhaps you've done those around him a disservice - now he bears no evidence of toolhood as obvious as a mullet!
If he took the stranger seriously, visited the website, acted on the well-meant and accurate advice, and months later remembers the stranger well enough to buy him a round - I'm going to say that that's pretty good evidence he is not a tool.
I think there's something to be said for telling people hurtful truths that can be quickly remedied. If broached appropriately and with a right-minded heart, I think a comment about your haircut would have been taken just fine - because of the temporarily and ability to instantly or quickly be solved, it's not as offensive, and actually, it ends up being quite helpful. Like having body odor in one moment or a huge stain on our shirt.
However, if that solution takes time to be alleviated, such as being grossly overweight, ugly or simply stupid, these kinds of "honest truths" will cause true harm because they will cause strong self-esteem hits that will linger over time. I for one would be happy and want with these kind of "temporary hurtful truths" told to me. I would like to say I would be the same for the long-term ones, but I'm sure I would be truly hurt just the same.
Regarding 'grossly overweight' - every fat person knows s/he is fat. You're not telling them anything they don't know. And you're not going to give them an incentive to lose weight by doing so.
That's not even near true. Many people are completely oblivious about their weight. Though I highly doubt you will do anything but hurting them by telling them that they're fat.
Body dymorphia is a very real phenomenon, although it's commonly seen the other way around. As a formerly fat person, I have to say that I'd go long periods where I'd be willfully oblivious to my weight. The occasional hurtful comment and/or painfully bad photograph really did jar me into action.
Body image isn't always accurate. Surely you have heard of anorexia?
Clip from white chicks about that (opposite of a fat person thinking they are not, but similar principal I guess):
http://www.youtube.com/watch?v=6Gy4xMgArmk (dressing room scene -- possibly NSFW)
I hate to glom onto just this example, but I've ever so gently suggested to a fellow who wishes to advance in his endeavors that maybe he might find it worth his while to pay more than $10 for a haircut. The response was a pretty miffed retelling of a time he paid $30 in San Diego, and it looked "just the same." (I wondered if it were possible he couldn't tell the difference between qualities of haircuts, being that his appearance suggested that.) The lesson I took from this is that people chose the haircut they have and they're likely happy with it - the alternative being that they don't care. Your differing tale intrigues me.
