It's the old leftist anti-gun standby: Pretend as if the 2nd Amendment was drafted only to protect hunting and self defense against criminals. Ignore the fact that the Founding Fathers explicitly created gun rights for the purpose of repelling and overthrowing a corrupt government. Pretend as if Americans are not supposed to have access to military grade weapons when that is exactly what the 2nd Amendment was enshrined to protect.
Under the Constitution, the American militia was intended to act as the defense force for the nation. And, the militia was made up of every able bodied male citizen. The militia was the military (in a sense), and the militia had access to all the weapons needed to fulfill their role. This included repeating rifles (automatic rifles), cannons, explosives and even naval ships in private hands. The Founders never intended for a standing military to exist, nor did they ever intend for a standing military to act as a proxy in place of an armed citizenry.
As James Madison noted:
"Besides the advantage of being armed, which the Americans possess over the people of almost every other nation, the existence of subordinate governments, to which the people are attached, and by which the militia officers are appointed, forms a barrier against the enterprises of ambition, more insurmountable than any which a simple government of any form can admit of."
- James Madison, January 29, 1788, Federalist No. 46