Why not? If the 2nd amendment is in place to prevent the need for a standing army by allowing for militias to exist and serve as the defense force therefor the maintenance of a standing army is unneeded. The other option is that you support a standing army which is a tool of oppression.

Either you support the 2nd amendment as a means of national defense or your support handing the tools of oppression to the government, per the founding fathers.

Where did you get the idea that the only purpose of a “well-regulated militia” is to completely replace a standing army? Just because some of the founders were against the idea of standing armies doesn’t mean that they saw it as an “either/or” proposition.