Just because many politicians are ignorant about firearms types and nomenclature doesn't mean there is no way to tell them apart, or that there is no good reason to control or restrict them. You could always hire an expert to make these distinctions, in fact, that would be a way to get the NRA involved in the process. There are lots of ways of regulating what is "street legal" on automobiles, aircraft have performance classes, sailboats have industry standards that indicate different levels of seaworthiness offshore, it wouldn't be any harder with guns. Just the few simple requirements I listed here; length restriction, magazine capacity limits, a sear design which could not be modified to "full auto", would get a lot of these weapons off the market. By far the greatest factor is magazine capacity. The "full auto" mode isn't very useful, even on the battlefield. It is great for killing a man in a phone booth, but in a gun battle you would be better off staying in single shot mode. Your ammo would last a lot longer.

Maybe liberal politicians can't tell the difference, but gun consumers are smart enough to not buy a weapon that only looks like an assault rifle but can't do the job.

Remember, the idea is not to make accident or murder impossible, that is totally unrealistic. The idea is to make them less likely and less lethal. If you're determined to dismiss the concept outright, you can always conceive of a situation where it would not apply. We don't sell people bazookas because you can also kill with a knife.