Semi-automatics still fire a bullet when you fire a trigger, you just don't have to use your hand to pull a piece of metal back and forth. There are bump stocks that can make it worse, but that's not on the table.
What makes it an assault weapon? Semi-auto fire rifles coloured black?
If it shoots one bullet for one pull of the trigger, I don't see how that makes it military style? Militaries use full auto, that's already heavily restricted.
Semi-auto hardly makes it a mass murder gun? A pump action shotgun can fire pretty fast, some people are great with bolt-action rifles.
Is it only rifles? Should they ban semi-automatic shotguns too?