Language changes. (Or in Torvald's case, devolved.) 'Well regulated' just means 'well equipped' in modern parlance.

Any attempt to try and claim this means 'Only the mitliary dur hur hur' should be met with 'Tell me you've never opened a history book in your fucking life without telling me'.

Mock them ceaselessly for being idiots. Heckle them for their lack of knowledge. People like this completely abhor being considered less intelligent than they think they are. It's why their go-to insults involve declaring conservatives to some variant of 'dumb'.