The segment takes about 18 minutes and I highly recommend it. But here's the quick summary: a right-wing blogger who incited people to throw rocks through the windows of Democratic party offices cooked up a conspiracy theory that the Obama Administration seeks to overturn the 2nd amendment by not going after anyone's guns but by following through with a sting started during the Bush administration to attempt to track suspicious gun sales. The guns in question will (according to the theory) lead to more gun violence which will justify stringent gun control. Not kidding, that's the theory, and Members of Congress have taken this ball and run with it. You see, they're going after your guns by not going after your guns - yet. Sneaky liberals!
To describe how this sounds to her, Maddow told the most wonderful story about a long bus ride in which the person sitting next to her spent the whole time talking loudly into a cell phone. At the end of the trip Maddow noticed that the "cell phone" was actually a hunk of aluminum foil crumpled then fashioned into the shape of a cell phone. Fox News and Republicans have reached that point in crazy.
Maddow's summation of this phenomenon deserves a full transcription:
Fox News and the right wing echo chamber that it elevates is an important phenomenon in American politics. There is a whole world of news and things that are presented as plausible over there that do not translate at all to the rest of the world that does not watch Fox News. But inside that bizarre, factually suffocated bubble of opportunistic, paranoid, cockamamie, fact-less, break-their-windows nonsense is most of the republican party of the United States of America. [emphasis mine]
The whole segment: