Self-esteem is your opinion of yourself; high self-esteem refers to a feeling of confidence or happiness with one's self. It has absolutely nothing to do with other people, what they say or what they think. It's all about you.
Low self-esteem has nothing to do with basing your worth on what other people say. It simply means that, as an individual, you don't think you're worth much. As a matter of fact, plenty of people with low self-esteem receive compliments on a regular basis. When they hear these kind words, they usually deflect them or twist the meaning until the message aligns more closely with their view of themselves. So whether or not you are capable of ignoring the insults of others has absolutely nothing to do with your esteem issues because, even if the words are kind, a person with low self-esteem perceives them as dishonest or inaccurate.
Low self-esteem is actually worse than depression, because the person trapped behind it truly believes they deserve all of the sorrow and unhappiness they receive. It is a loathing that is completely independent of the world around you; it's trapped inside your head. No stranger can make you feel better, no stranger can make you feel worse because you already believe the worst things they could ever think of to say.
In modern psychology, it is believed to be healthy for a person to have a positive self image, a natural optimism. This seems, to some, to be madness. If you are not an outstanding or noteworthy person, why on Earth should you fool yourself into thinking so? If a person truly has nothing going for them, why should they pretend? The only answer I can think of is that, without hope, all else fails. That, as human beings, our survival depends upon our ability to see a bright side, a happy ending, the last smidgeon of a chance. People with low self-esteem cannot see that in themselves. There is no greater hell.