The basic argument of the Left, that 'assault rifles' are not necessary for personal defense, is correct.
I’m sure Fidel Castro would have agreed with you, see:
Fidel Castro’s “common sense” gun control pitch
JWKOur Founders intended ordinary citizens to keep and bear arms [a contemporary fire arm used by foot soldiers] so they would be ready and able to defend themselves against a despotic government if necessary. The AR-15-semi is a civilian version of the United States military’s M16 and ought to be kept by ordinary citizens to defend against a tyrannical government if necessary. Forewarned is forearmed.