Metro police departments across the country are all too well funded with military-grade equipment and too well trained. Feel like you need heavy guns to fight against their abuses of power is always a losing proposition because that's a battle they're designed to win. Most successful pushbacks against police departments have come through political pressure and broadcasting their abuses in the public discourse. So no, citizens don't need assault-style weapons to protect our freedoms, we have other means for that.
See that's the thing -- they've convinced you that's true. I don't mean this from some nutcase point of view or something. I mean literally a bunch of people in the desert with AKs and RPGs wreaked havoc on the US Army for years in Afghanistan, Iraq and elsewhere. There's plenty of history that undermines your assertion.
At the end of the day, police depts and law enforcement is NOT equipped to handle mass violence, they are equipped to handle specific levels of crime. This idea that they somehow are equipped to handle a war against an entire municipality is BONKERS.
They would never stand a chance against a nation of 400M arms fighting in urban warfare. Nevermind the sabotage and acquisition of those very weapons by the folks fighting back.