I would respond that there are 270 million gun owners in the United States. There are 1.4 million active members in all of the U.S. military. So the government is outnumbered by more than 268 million guns and people — fathers, sons, daughters.
I would also guess that of the 1.4 million service members, not all of them would be willing to use their weapons on their parents, brothers, sisters and neighbors.
I expect the letter writer himself would not use the 155 mm Howitzer he mentioned against his own wife, daughter or son, just because the government decided to reject the Second Amendment of our U.S. Constitution.
God bless America, and get the government off our backs.