Student or Learner
Is there an idiom to describe when you are trying to explain a concept/idea to an individual who understands but is being ignorant because he/she wants to give you a hard time?
A friend suggested "Don't preach to the converted" but that is not what I am looking for. In the case I have described, the person will not be influenced by any kind of persuasion. Something along the lines of an idea "falling on deaf ears".