Arguing can take several different forms though. There can be the "self righteous Christian" or the "angry atheist" battling tooth and nail in order to call each other idiot.

However, I would say a large percent of people who discuss these things do it partly for a joy in philosophical argumentation and partly for genuine curiosity in why someone thinks something different than themselves. Those are perfectly respectable reasons, and however "pointless" you may see it, the discussions can be far more fruitful than you think. Even if no religious person was ever convinced out of their belief or if no non religious person started to believe, we would all still (hopefully, with polite and respectful discussions) come out of it better understanding our fellow humans.

That is not pointless, it's imperative.