Wonders

I have a very innocent view of the world and I sit here and wonder why as I have been brought up with the attitude "treat people as you would want to be treated yourself"! Sounds lovely and is something I try to enforce in my every day life, when I'm feeling miserable inside and somebody wants to tell me their troubles I listen and think well I would like somebody to listen to me.
So I wonder why I allow myself still after many years to be treated by people like dirt, why do I allow people to speak to me one day, then snub me the next?
Is it too much to ask that people treat other people with the respect that we all deserve?