Whats so special about assault rifles?  If you want home protection, just use a hunting rifle, shotgun, or a handgun.  Fully automatic weapons are just going to get you, your family, or innocent bystanders killed.  The only countries I know of that commonly allow fully automatic weapons are African hell-holes, where the life expectancy is about 36 years old.
Theres a mentally ill and partially autistic guy I work with whos a big gun enthusiast.  He goes to machine gun shoot-outs and wears fatigues to work every day.  Hes a ticking time bomb.  And I am pretty sure he has several guns.  Laws need to be in place to protect innocent people from guys like this.