The problem comes when the person is unaware that they do or behave in any particular way, which is entirely subjective and open to interpretation anyway, or they are unwilling to acknowledge the presence of a blind-spot. Which may or may not be considered by them as perfectly normal/okay - that's why it's subjective.
The real problem is when they see that action or behavior normal/okay for them to do/be towards others, but not when it happens the other way around.
A simple ideal that may be useful for each party to adopt could be - "do unto others as you would like done unto you".
Although, this is still flawed as it is still open to interpretation, as again "do unto" is completely subjective from both parties.
What be the solution? Attemping to understand, and apply some form of reasoning to establish what middle ground may exist?