It's not like I think this is a huge story, but nutty theories are fun, so:
There is a meme going around the blogosphere that MS-NBC might not have edited the video of the guy toting the AR-15 to carefully disguise the fact that he was black--a video that the anchor presented as an example of possible . . . white racism. You see, one CNN reporter says he saw someone else with a rifle at the rally. (CNN refers to it as an "assault rifle", which is totally inaccurate. Assault rifles are full auto, and thus illegal for civilian possession in most cases. The AR-15 is semi-automatic, meaning that you get one bullet fired per trigger pull. This is mostly a digression, except that it does go to show that the CNN reporters are not exactly crack weapons experts capable of reliably identifying the guns they see.)
Here's the CNN video, which I expect most of the memesters found via The Daily Show:
No one else saw this guy at the rally, as far as I can tell, which the local paper reports as being a dozen strong. But say he was there. What are the odds that he happened to be wearing exactly the same thing as the African-American guy carrying an assault rifle, down to the pistol on his right hip? Did they buy the outfit from the same designer?
Look at the video above, and then check out the MSNBC footage:
This is entering into the level of implausibility embraced by those who defended the Rathergate Memos. Yet I've seen it stated as a positive fact in several comment sections.
But here's how we know, beyond a shadow of a doubt, that the footage was not of the protester's white doppelganger: you can see the CNN reporter in the MSNBC footage. Yet that reporter makes it clear during the interview that he did not see the mysterious other guy who was identically dressed and armed, but possibly white.
There is no reasonable doubt that MSNBC cropped the guy's race out of the video with some extremely weird editing. I don't know whether the anchor knew about it or not--I presume she didn't--or why they chose to edit it that way. But the evidence is pretty overwhelming that they did, and that at the very least, the anchor made some stupid and unwarranted assumptions.
The guy carrying the gun, by the way, was not a rage-filled lunatic looking to take out the president. It was a publicity stunt staged by a local (libertarian) talk radio host.