I have a couple of niggles, let me know what you think:
There is often some dispute over what postmodernism is at its core, so it might be an idea for you to include this so that the refutation you posted by Chesterton has some context.
How can this irrationality be called the face of rationalism when it so tragically flawed?
I believe the statement behind this question will be the subject of the first few pages of debate. Having explained why you think it is irrational, you should probably explain why you think that postmodernism is called the 'face of rationalism'. You're only going to have to do it anyway, I think.