Most people simply do not know their right way from their wrong way.
Once I got into an argument with a friend about this issue. He refused to believe that riding on the right is correct. I showed him a copy of the clause in our state's motor vehicle code in which it plainly states that bicycles should ride on the right. Incredibly, my friend still refused to believe. His belief in riding on the left was so deeply ingrained that he refused to change his mind even in the face of the clear and authoritative evidence of the law itself!
I doubt that it is productive to argue the point with random riders that you meet on the street.