The 2nd amendment just says the government can't take away your guns. It doesn't say anything about it being okay for you to use them against the government.

I mean, hell, police kill people all the time, but the courts treat having a gun on your person as a reason the cops had to shoot you. So they can't take away the gun, but they can take away your life for having it.

Basically you can use it as a security blanket to rock yourself to sleep at night, but get anywhere near the gestapo with it and you die a "terrorist."