Prejudice leads to false character building.
Being judged or labeled may be inevitable. And while it happens, the judged eventually become what they were branded for because other people approached them as such.
For example, if we believe that all blonds are dumb, we will most likely talk to them as if they really are idiots. We approach them as such, they respond appropriately, then we respond back, they respond again and then us and then them and so on.
Characters shape up because sometimes we unknowingly look for the character we believe a person is suppose to be, usually based on how we first know or heard of him/her. In our exampe, the process created the "dumb blond" personality.
And if at the first attempt the dumb-blond-theory failed, some may opt to persist and insist. And the cycle goes on. We decide to stop only when the judgement is proven. Unaware that we are simply satisfying an equation that didn't exist.
Hasty conclusions. A self fulfillment prophesy. It's a recurring pattern yet we still fail often at it.
We never learn.