You're the one being unrealistic.
While we would prefer if the government dealt with the "bad guys" for us and we would not have to, the reality is that government itself always also is or turns into the "bad guys".
If you pay for full auto for the government with your taxes, then you have to also ensure enough ordinary citizens have them as well, so that we do not end up like the Weimar Republic.
And anytime you allow government to get a monopoly on weapons, you eventually always end up like the Weimar Republic.
Sure there are always going to be some people who can not control themselves and can't be trusted with a full auto rifle, but those people also can not be trusted with a car, flammables, explosives, toxins, or anything else that all people have easy access to.
So the only way to deal with those dangerous people is to confine them under supervised conditions.
To instead try to turn the entire civilian population into a supervised condition that is denied access to full auto rifles, is to ensure a dictatorship.
There is no option.
Gun control does not work, never works, and is inherently in conflict with any democratic republic.
Read any history book, and they all tell you that all governments become corrupt over time and have to be destroyed by force.
It is inevitable, with none lasting longer than about 400 years, and most less than 100 or so.
The US government is no exception, and has been evil to the point is should have been destroyed, over 100 years ago, like the Spanish American War, the Philippine Rebellion, etc. The only reason we have not already been forced to act is that the corruption has been mostly aimed at people outside this country. Like Vietnamese, Iraqis, Libyans, Afghans, Egyptians, Syrians, etc. But there are millions being harmed in the US as well, such as those imprisoned by the illegal War on Drugs.
Just read the Bill of Right again. It is very clear. There can be no legal federal gun control laws. Totally impossible. And yet there are federal gun control laws? How is that possible, and why did we let that happen?