When somebody talks down at you - tell them that they are right and walk away. What you are actually doing is mocking them in a nice way but they won't realize it because you will say it in a serious way to make them feel good about themselves.
If you start to stand your ground and fight back however, you will feel silly one day thinking back to the time you spent fighting with an idiot. If you fight with an idiot - what does that make you?
Just picture yourself shouting at a banana on the table.