The second amendment has nothing to do with "allowing the government to prohibit weapons". The second amendment protects from federal infringement. If some weapon is not protected or if some individual's right is not protected, that doesn't allow the government to prohibit. Where do you get that?
The federal government cannot prohibit something unless it was given the power to prohibit by the states.
By your assorted assertions, the 2nd Amendment serves no purpose whatsoever.