I suspect you just want someone to argue with...if that's what your after, get married. If you are already married, and haven't found someone to argue with, what's your secret?
To answer your question, agreeing to disagree doesn't necessarily mean you are apathetic, in general; just apathetic to what the individual you arguing with thinks. Take me for instance. I could care less about most thoughts manufactured outside of my head. And therefore I can avoid most arguments by the simple knowledge that the individual I disagree with means absolutely nothing to me in the scheme of things. That's not apathy; it's simple logic. If they are not impeding on my freedoms, are not hurting my family in any way, what they think simply doesn't matter. Furthermore, what people think is a product of both their experiences, the friends they choose, the family they come from, the genetic imprint of their parents, and their environment. Since those combine to make someone completely different from me, it really isn't any wonder that we don't agree on everything. And since its almost impossible to change what another person thinks, why would I waste my time trying? Not apathy; just good ole' fashion good sense.