The defense can argue that while crying "Fire" in a crowded theater can be reasonably expected to cause harm to persons therein, the mere posession or manufacture of a machine gun, absent the criminal misuse thereof or reasonable expectations of such criminal misuse does not present a reasonable expectation of injury to other persons or to the public in general.
Also, crying "fire" in a crowded theater when there is no fire is not speech it is the equivalent of assault. Crying "fire" when there is a fire is necessary speech. Being silent when there is a fire in a crowded theater can be considered negligent malfeasance. None of the above is political speech which was the target of the first amendment. Just as the second amendment is about individuals bearing arms for homeland defense. In the 1A congress is prohibited from making any law, etc. But in the 2A the INDIVIDUAL right is spelled out and assumed to exist.
Yes, that will be the defense response. But the prosecution will have already made the case that reasonable curbs may be placed on individual rights even to prevent a future harm. Giving a 6 year old a firearm doesn't necessarily mean he will harm himself or others, but reasonable laws can prevent a 6 year old from ownership and use. Just as the 14th Amendment guarantees equal protection of the laws, it does not require that felons have the same privileges as others. Yet a felon might not do any harm if permitted the freedom.
It will come down to whether ownership of a machine gun can reasonably be considered an unfettered right, or whether the state has the power to regulate its ownership and use, as it does in other rights issues.