As to legality, the bad guys are doing it, why not all of us?
I would only find that argument compelling in the context of advocating for the complete overthrow of the current government. Otherwise it just sounds an awful lot like LARPing of the same sort that… well, militia movement types who glorify Ruby Ridge engage in.
If you want the fight to be more even, guns are a fucking waste of time. You’d need armed drones dropping grenades like in Ukraine. Or IEDs like the insurgents in Iraq and Afghanistan.
The cops already assume too many houses are armed up like ruby ridge and they go in no-knock warranting and shoot your dog while blinding and burning your toddler “just in case”.
The more guns proliferate the more on edge we all get, and cops aren’t the ones that are gonna be more respectful with more people armed. Quite the fucking opposite has been true so far.
The alternative is simply trusting the state will wield their violent powers fair and justly.
There are numerous steps one can take to provide oversight to the actions of a state that do not include a literal arms race between the civilian population and the state. I would go so far as to say that civilian firearm ownership is near-negligible in terms of threats that a state actor can face, and that glorification of civilian firearm ownership as a means of ‘preventing tyranny’ is exactly the kind of atomized and easily-struck-down approach to dissent that right-wing governments encourage.
Put it this way - if things get bad enough that you’re planning a shootout with state forces, the point where individual acquisition of an AR-15 would make the difference has long passed.
So the arms race just needs to continue!!
The private militia needs tanks! Missiles! Fighter jets!
…come to think of it, I guess Mexican drug cartels are pretty much the libertarian wet dream.