OKAY. So if the military won't fire on US citizens, and even if they do, they have planes that can drop bombs and a whole other assortment of fancy equipment that makes owning a gun useless, why do people need guns? What "right" is there? Do you need to own a gun just to have it? Why do people feel the need to own something designed to kill other people?
I don't get it.
The second you engage a conservative in a hypothetical argument about fighting against an imaginary tyrant, you've already lost because you are arguing against a strawman. Nobody is proposing confiscating guns, or making gun ownership illegal.
Instead, the argument is about where to
draw the line. For instance, nobody believes citizens have the right to own tanks, jets, rocket propelled grenades, etc. If you get the conservative to follow his logic consistently to the conclusion that citizens ARE entitled to tanks and jets (to be able to fight against the military), then you have won the argument by making him look ridiculous. If you get him to admit that the only real issue is line-drawing, then you have elevated the discussion and can have a sane discussion without all the tyrant talk.
As a general matter, I've noticed that reductio ad absurdum is a great technique to use against conservatives, because they like portray complicated issues as having simple solutions usually stemming from emotions. These kinds of emotional views are easily taken to the extreme. The argument technique does not completely defeat the conservative, it just gets them to argue better. For instance, if someone says "government should stay out of private industry" it is easy to just list all the horrible consequences that would result (ie. no inspection of food or drugs, no licensing of doctors, tolls on every road, no government contracts for private companies, etc.). This shifts the conversation into the more nuanced and liberal-friendly "how MUCH government should be involved in private industry?" or "how MUCH regulation is necessary?"
Almost all of policy-making is just finding the right way to draw lines between competing interests. Conservatives hate portraying issues that way. As a side note, I'm obviously only talking about extreme conservatives. There are plenty who you can past the absurdum argument and go straight to a reasonable discussion. I've noticed the gun issue makes them all kind of nuts though.