One argument for not taking guns away, is that "We need them in case the government becomes evil and we need to overthrow it."
Alright, say that's true. And say literally every man, woman, and child is equipped with an AR-15 and unlimited ammo, how exactly are we supposed to over throw one of the worlds largest armed forces? How are the common people, even armed with unlimited ammo supposed to go against drones, powerful bombs, aircraft, tanks, etc. Sure, a small handful of military vehicle are owned by civilians, but those aren't going to last long. The general population is hopeless to stand up against death from the skies; not to mention all the possibilities of bioweapons or simply shutting off the utilities the government controls.
Perhaps in the musket days the general population could overthrow the government via force, but I don't think it's possible in today's world.
You do realize that about half the states would probably defect, and those states have tanks, and drones, and bombs. Your argument holds no water. Under your logic, all the soldiers should stop carrying guns too. What's the point if they have tanks, and drones? Stupid. Small arms are the key asset to overtaking a larger force. You ambush key targets, steal all their shit, and go back into hiding. It's one of the oldest tactics on earth, and just as effective now as it was in the Bronze Age.
Name me one revolution that's happened in the last 100 years where an armed populace defeated a dictator without military aid, internal or external (or, at the very least, the military sitting back and allowing said revolution to happen).
Go ahead, I'll wait. ---
Kill 1 man: You are a murderer. Kill 10 men: You are a monster. Kill 100 men: You are a hero. Kill 10,000 men, you are a conqueror!