What it actually says is that a militia is necessary to protect a free state. Then and now, “militia” generally refers to those non-professional soldiers that may be called upon in times of great need. This would seem to at least cover everyone subject to the Selective Service Act, which is a large percentage of the male population.

There’s also an argument that the 2nd amendment envisages a potential need for the populace to defend themselves from the government, as was considered necessary only a few years prior to its enactment.