The necessary and Proper clause has ever been used harm anyone or anything. It was used to justify the the regulation of production and consumption, it was also used to justify federal criminal laws.
We need a standing army because in time of war we will be automatically prepared. The anti feds wanted a militia, but this was proved to be ineffective. A militia would not give us enough time or resources to prepare for the war that would come.
The constitution states that we still have state militias. We wouldn't use a standing army to stop rebellions towards the government.
We, the federalists, want a big democracy. We believe that the uneducated majority can’t decide what to do in complex matters because they simply don’t have the ability to. The well-educated elites should have the responsibility of that job.