The poster you're referring to appears to believe that the States have been given the power to decide which weapons qualify as suitable for militia use. He is basing this on a Supreme Court decision. He most likely lives in a state who's gun laws and government officials are agreeable to him. He probably figures that if you don't like your state's gun laws and government officials, you should move. Fair enough.
The first problem I see is that the judicial fiat in question is unconstitutional, and just the sort of thing that the militia was put in place to counter. The second problem I see is that nothing in his thesis is preventing his state, and every other state, from becoming a state who's gun laws and government officials are disagreeable to him, and everyone else. Once this happens, there is nowhere to move to.
The authors of the Constitution, men who have referred to politicians as always evil each and every time, weren't naive enough to believe that state government would always be behind the people, and only federal government can be corrupted. Since the signing of the Constitution, politicians have been trying to take power away from the people and transfer it to themselves. They have twisted the words of the 2nd Amendment by adding things, like an act defining a militia, after the fact. Soon, they will move on to twisting the definition of a free state. So if a state isn't free, then a militia isn't necessary, right? What constitutes a free state? A judge will just have to tell us, right?
This kind of slavery to judicial rule is what enables courts to legislate away our freedom. Nobody puts judges in their place when they cross the line. The judge in the above referenced decision just wanted to do society a favor and put away an obvious criminal. Unfortunately, he misused his power in order to do so and ultimately caused a crack in the Constitution. The same thing happened in that contraception decision. With the benefit of hind-sight we now see the horrible error that's been made, and it is now up to us to correct it through the NRA and other organizations.
That silly 'it's not a weapon fit for a militia' argument is just an old gun-grabbers trick. Nobody should decide what weapons we can keep and bear, because it is only a matter of time before the decision becomes *no* weapon. The inevitable 'tactical nuke' argument that gets dragged out when this is said has no merit. The cost alone to build or obtain such a weapon is in the domain of only a handful of citizens. Citizens who are so rich and powerful that, if they really wanted to, could get a nuke regardless of laws.
In U.S. v. Miller, the federal government won the chance to bring Miller/Layton to trial. Had they in fact used that opportunity to do so, the question of whether a sawed-off shotgun was suitable for use in a militia could have been put to the jury. For some reason, however, the federal government decided it didn't want to put that matter before a jury (it could have done so in Layton's case). Indeed, I can think of no other instance where the federal government has gone to the Supreme Court seeking authority to prosecute someone, and then offered a plea bargain, for 'time served', immediately after winning.