Part of the reason people develop social anxiety is they are "brainwashed" into it by other people, circumstances, or events. For example, a child could develop social anxiety by their parent "brainwashing" them with constant criticism.
Others may be brainwashed by how they were treated in school or by life requirements that were too scary at the time (i.e.. speeches, being put on the spot, blushing, strong feelings of self-consciousness).
We can't do anything about the cause-- we are not time travelers. However, we can do something to change how we were brainwashed. The things we believed that are inaccurate and irrational are lies. They are simply not true.
We can learn to "wash our brain" of this irrational conditioning. We can learn to believe the rational truth.