Explain the need for military-grade fire power.
Explain how the word "need" comes into play in a free society. I own hundreds of T-shirts and many, many dozens of jeans. I have 35 computers, and my tool shops could put Home Depot to shame. Do you believe I must explain a "need" for all of these things? Perhaps you believe I don't "need" so many jeans, or computers, or tools.
By the way, FEW Americans have "military grade fire power." We have AR15s. We have AK47s. We have 30-30 rifles, 30-06 rifles, .308 rifles, and even .50 Caliber rifles. Ask any REAL soldier if he/she would go into combat with an AR15. They'd laugh you back into your mother's basement safe space.
Aside from that, the RKBA is all about the average citizen owning and maintaining the same firepower that the ordinary foot soldier would carry. So when you bother to study the supporting documents, and EDUCATE yourself about the true meaning of the Second amendment, you will ask,
"Why CAN'T American citizens own M16s, 60 caliber belt fed weapons, and flamethrowers?"
Don't feel alone. Lots of people have a fetal underdeveloped childish fear inanimate objects like guns. They are called HOPLOPHOBES. You might even count yourself among them.