Generally, when I'm in discussion with a believer I am civil, attentive, and open to new information. That said, when confronted by a Biblical Creationist, I allow myself to lapse into what can best be described as good natured mockery.
What else am I to do when told that the reason why the T-Rex had sharp teeth was to allow it to break coconuts? Or when taught that some dinosaurs laid eggs in straight lines whilst on the run, and in order to flee from Noah's flood? Or that Adam and Eve were real people, and that there really was a talking snake, and a garden, and a special tree that Eve really shouldn't have been caught scrumping from? Am I really meant to smile and nod when, in all earnestness, I hear that every single species we see today is a descendent of creatures that took a long ride on Noah's boat? Or that the Grand Canyon was formed rapidly due to the flood waters that had engulfed the Earth?
I'm sorry. I can't do it. I can't listen to it with a straight face. Furthermore, I think it's important that we don't. There are times when mockery should be deployed, and when it's ok to laugh out loud, point the finger, and pull a funny face in the direction of those seeking to convince you that any of the above could be true.
The real problem is that you are dealing with a person so utterly indoctrinated, so wholly (Holy?) immersed in the comic book more commonly referred to as the Bible, and so beyond reason and persuasion, that whatever you say, whatever evidence you proffer will be, has to be, tossed into the intellectual mincer of Biblical literalism. Scarily, these people are abundant, and worse, they want to feed this inanity to children. I know that I've banged this drum before, but it matters. Science is the best tool we have for figuring out both how the world is and how to improve it. Religion in any guise is unfit for this task, but Creationists are particularly nefarious. So when I mock these people, when I laugh and expose them for what they are I undergird this with the knowledge that I'm doing the world a favor. These loons need to scurry back to the caves from whence they came, preferably taking their silly books and ideas with them. We should then roll a large stone across the entrance and perhaps get a couple of guards to ensure they cannot escape. They can then continue to impersonate the Mad Hatter for as long as they so desire, leaving the rest of us, those of us who actually care about what's true to start solving some of the problems that cripple our wonderful world.
Rant ended. Move along. Nothing to see here.