I want to amplify the point made above that YEC is social and political. The argument is not about what it seems on its face. If you look at the history, you'll see YEC is, well, "young" itself, fairly recent. It is a reaction against what is seen as the breakdown of morality, etc, etc.

Darwin is the primary enemy there, followed by cosmology, but any "fellow travelers" will be attacked as well. For example, they wouldn't have any beef against say applied EM theory, unless some link between that and Darwin and cosmology comes up. Their belief is that Darwin lead to a rejection of God, which is leading society down the toilet morally.

And that's why you can't argue with them. It's not about how old the earth or the universe really is. They don't really care. It's just a proxy for what is the real bone of contention.

-Richard