This is supposed to be a Constitutional republic, supposedly in which the rights of individuals are not subject to being voted out on a whim by a tyrannical majority, even if they just "wanna feel safe".
The 2nd Amendment says, "The right of the people to keep and bear arms shall not be infringed." If I have to get a government background check to use my buddy's shotgun, AR, or Glock, that's an infringement. If I have to get a background check to buy a gun, that's an infringement by the government on my rights.
It is not the government's place to say who should or should not own a gun, unless that person is a convicted felon. If government wants to provide a list or a database of convicted felons where people can check a potential buyer if they want, that's fine. But the SECOND the government is in charge of denying you a gun sale, that's an infringement. See the difference?
That is the 'camel's nose under the tent'. It allows government to get involved with its licensing and background checks. Once involved, they never go away.