That argument is so wrong on so many levels. Effective law enforecement is great, but the most efficient operations will never prevent all crimes, so why would they take away the enumerated right of people to fend for themselves when the LEO's are not present right then and there? Even if it could be shown that less guns means less crime, and the evidence seems to be contrary to this, it still is a violation of liberties to enact these anti-gun measures.
If it could be shown that 95% of deaths from car accidents would be saved if the speed limit was 10 MPH, would we want that? And driving a car at any speed is not even an enumerated right. Violating the BOR's is itself a crime.
the 2A doesn't prevent "all crimes" either.
you can get a gun legally in NYC.