Actually I think the logic is something like, "whatever the government is likely to use against me in a realistic scenario is something that I should be able to use to defend myself against them." It is highly unlikely that the government would be trying to use nukes, artillery, tanks, or bombers against little 'ol me. Why bother when a single 22 handgun would be sufficient?
When the police/SWAT and FBI stop packing heat then it might be okay to disarm regular citizens. Until then we have the right to defend ourselves with something more than good intentions. This is why I also object to trying to outlaw armor penetrating rounds. Cops and FBI agents will typically be wearing body armor and those rounds are necessary to defend yourself against them.
If the entire US army has orders to take you down having an entire third world army at your disposal would not be enough to save your life, but that is a straw man situation.