The point of an armed populace in term of protecting freedoms is for the people to have enough combined firepower to make tyranny impractical. It's been proven time and again that an armed citizen insurgency can defeat the US military.
If 150,000 armed Democrats in Minneapolis started taking pot shots at ICE any time they saw them, there would be nothing the Trump admin could do short of nuking the city.
But if I had been there on Tuesday with my gun and started shooting at ICE by myself, all I'd have accomplished is getting myself killed and giving Trump more ammunition.