Self-esteem and self-improvement

A recent discussion about transsexuals made me wonder about the gap between our desires and reality, and in which cases it is considered socially acceptable to correct reality, and in which cases it is considered more appropriate to correct one's desires.

I don't mean the blatantly obvious cases, such as that I would like to see one of my daycare teachers dead, but am not allowed to make that happen. I was thinking more along the lines of clear disapproval of cosmetic surgery that a lot of people express, vs. lack of same disapproval of cosmetic dentistry.

Pretty much every conversation about cosmetic surgery turns to lack of self-esteem (which in our culture has pretty much turned into an insult, usually having very little to do with the actual self-esteem of the person, or lack thereof) and evil cosmetic industry preying on people who are clearly too stupid to decide for themselves. I have never heard the same feelings expressed about dental braces (I realize that a lot of people have other reasons for those than cosmetic, but a lot of them are used to make teeth look more even) or tooth whitening.

I could never quite understand why a person who wants a perfectly straight nose is suffering from a low self-esteem, has been brainwashed by society who values women only for their looks (or by society who values people only for their looks, in case of a man), needs to learn to love and and accept herself/himself as he or she is, needs to understand something about the inner beauty, etc. A person who wants perfectly straight teeth, on the other hand, is just a person who wants to straighten his or her teeth.

BTW, isn't "low self-esteem" supposed to mean "evaluating self-worth, at least on some parameters, as lower than it objectively is"? Why are people who say that they are ugly automatically accused of having low self-esteem even when they are in fact ugly? Is it because failure to deride their self-esteem means that you agree with them?

Another interesting thing about alleged self-esteem and looks is that the words "low self-esteem" are used both about the people who are striving to improve their looks (they must clearly have low self-esteem since they are unable to love and accept themselves as they are, and must spend time and money on their looks) and the people who don't care much (they must clearly have low self-esteem since they don't consider themselves worthy of new and fashionable clothes, hairstyle or makeup).

Isn't it time to admit that the words "low self-esteem", at least when not used as some strictly defined psychological term, are just a simple insult that people use on their fellow citizens whose lifestyles they disapprove of?