HOW do they look themselves in the mirror?
That's just one of the questions I ask you, my friends....
I suspect they fall into two camps.
First, and by far the majority, are simply ignorant and/or stupid. They honestly believe what they've been told, and why not? What they're told is dressed up to look like truth, and it's terribly easy to sell a lie when the person you are telling it to desperately wants to believe it. Garbage in, garbage out.
The minority are indeed completely devoid of Human decency. I don't doubt for a second that they know perfectly well that they are peddalling lies - you couldn't work to make the lies convincing without knowing what you were doing. They seem perfectly comfortable with that.
I imagine they think they are working for a greater good. I imagine they think that getting religion into schools is the way to a better America. Either they think the world will be a better place with kids taught christianity in schools, or if you like conspiracy theories they see it as one step closer to a total theocracy.
Actually, in a way ID reminds me of a cargo cult. They've seen just how successful science is, bringing miracles that make theirs look pitiful in comparison. They think that by building their own version of it maybe that good stuff can be theirs. Thing is, they just don't know how to do it right.