What's the "IT"? Well, it doesn't really matter.
What's important is that the speaker has drawn a line beyond which they refuse to extend their own reasoning. So it's an impatience created by a lack of empathy. Why the lack of empathy? Well, either the speaker is mentally unable to engage or can, and doesn't want to.
The latter is understandable. I really don't find it comfortable empathizing with certain people, like racists, survivalists or creationists. But I do, and I'm usually glad I did, because if you take the trouble, you get terrifying insights into the human condition. I keep up a lot of correspondence from the militias and the really, really creepy thing is how much in common they have with friends of mine who have families and live in the suburbs. There's a lot of honesty, and something I value, curiosity too, in abundance.
But certain fears and certain psychosis have been bent into a hermetic worldview of internal coherence - it's just one that is impervious to the consequences of taking such a position.
Imagine meeting Richard Dawkins. Or a weblogger.