On Thursday evening, MSNBC’s Lawrence O’Donnell made a unique argument against the idea of armed guards or teachers in schools being able to take down mass shooters. Here was his genius argument:

So, just to get this straight, O’Donnell’s argument is that a bullet travels faster from an AR-15 than a handgun, and therefore . . . something. Perhaps O’Donnell thinks that mass shooters have Matrix-like abilities to dodge handgun bullets, where rifle-fired bullets would pierce them. Perhaps O’Donnell thinks that the adult with the gun is legally bound to challenge the mass shooter to a duel in which both shooters fire simultaneously.

But let’s do a bit of math.

Let's say a rifle fires at 3,900 ft/s, and a handgun fires at 1,300 ft/s. Let's say the two shooters are 100 ft apart. That means the difference between the bullets reaching their intended targets is approximately five hundredths of a second. So, presumably, O’Donnell’s argument is that it is entirely impossible for a guard to fire at the mass shooter .05 seconds in advance of the mass shooter, because AR-15s make you omniscient and omnipotent.

The only argument with regard to gun control that has any correlation to muzzle velocity has to do with the amount of damage to the human body caused by higher-velocity rounds. It is true that a round fired from a rifle does significantly more damage than a round fired from a handgun. But that has nothing to do with the capacity of an armed guard to stop a person with a rifle.

Leave it to MSNBC to screw up even this easy argument this badly.