If you really think that any gun will protect you from the government if they decide to fukk with you than I don't know what to say. You realize that the government will always have the upper hand and is leaps and bounds above your average citizen in weapons technology. If they want to exterminate you as a black man or anyone else for that matter they could do it easily no matter how many guns you have. They could send an unmanned drone to your crib and blow up your whole house from 30,000 ft in the air you won't know what hit you.
You have a much better argument if you want to argue about protecting your family against your average criminal. But just as you argue about that someone else arguing against could say that laws to get your hand on guns are too lax (aka its too easy for a lunatic to get their hands on a gun or a gun that could inflict more damage). What about gun homicides that stem from a sudden crime of passion and easy access to a weapon at that instance.
Banning assault rifles is a statistical argument. Long barrels have better accuracy and thus could cause more damage to someone or hurt more people because you could shoot someone from further out. Being further out means it'll take longer to discover the perp. Automatics also cause more damage because you could shoot more people in a shorter amount of time. These are just common sense arguments against these types of guns.
Let me tell you why what u said was dumb.
The government has technology, but at the end of the day they have to rely on soldiers (citizens) to use them.
If the government ever decided to turn their arms on citizens, an extremely large percentage of soldiers would defect before gunning down their families and friends in the streets.
If they then decide to bomb their citizens they risk the possibility of destroying infrastructure and putting themselves in a hole that will be almost impossible to get out of. Also the government will never be legitimate because the children and family of all those people you killed will be out for revenge. So a government critically in debt, with a depleted military, and a rebelling population leaves the door open for another foreign power to enter the fray and start siding with the rebels providing them with funding, weapons, and food. It will be an unwinnable situation.
The crazy thing about the above scenario is that this is a strategy the U.S and other first world countries have used time and time again with countries that have turmoil with their leadership in order to increase their influence in world affairs.
Trust me, governments are more afraid of citizen uprisings than you think they are. They don't really give af about a few random shootings and "protecting" people. They need a population that will willingly disarm themselves so they can stamp out any dissent quickly before it turns into a revolution