People who talk down to you are showing you their ceiling, not yours.

Contempt says more about the person handing it out than the person receiving it. When somebody talks down to you, they are describing the size of the world they can imagine, and you happen to be standing inside their description. That is their limit being read aloud. None of it measures what you can actually do.

The next time it happens, try hearing it as information about them rather than a verdict on you. You do not have to argue with it or absorb it. Take it to God instead, ask Him what is true, then get on with your week.