If you happened upon an argument in which both sides were declaring they are right, at the wrongness of the other, yet they were the same, you would have the title of this post.  

Imagine there is an argument.  One group of people is yelling, "We are the quarter!"  Then, on the other side, another group yells back, "No.  We are the quarter!"  The first group yells, "We trust in God!  We believe in liberty! We show the image of our Founding Father George Washington!!!"  The other group argues back, yelling loudly and fiercly, "No.  That is not what a quarter looks like!  A quarter has an eagle!  The bird of America.  Our country!  We boldly proclaim the United States across our top, because we are more partiotic than you!"  The argument goes on and on.  The first group says, "You can't be more patriotic than a founding father!"  Yes you can, they reply.  You can be a goddam eagle!  We wear our name!"

Yet, while debate goes on, and people double down on their rightness, someone points out that they are only one side of the same coin.  They miss this, though.  They fight from only their side, and thus miss the whole.