there's a big difference between so called assault weapons and semi automatics.
most assault or military weapons are automatic, that is you just hold the trigger and it keeps firing. the difference between an automatic weapon, which is designed to kill as many people as possible in a short time and a semi auto is huge, while the difference between a semi auto and a manual repeater is minimal.
There is no real reason for people to have military weapons, they don't serve any purpose other than discharging a large number of projectilse in a short time, something which can only have one purpose.
In saying that, the banning of them still will not address the real problem, and that is what causes people to flip out and want to kill as many people as possible. But as usual no one seems to want truly solve the problem, but take the easy, simplistic PC approach and seem to be doing something so as to keep the narrow minded masses happy.