People rarely deny that “Assault Riffle” is a thing, because it’s very strictly defined… per your own sources

Assault Riffle

By U.S. Army definition, a selective-fire rifle chambered for a cartridge of intermediate power. If applied to any semi-automatic firearm regardless of its cosmetic similarity to a true assault rifle, the term is incorrect.

People do however deny that assault weapons are a thing, because of how loosely and interchangeably they are defined. Also per your own sources:

Assault Weapon

Any weapon used in an assault (see WEAPON).

So if I hit someone with a crowbar, it’s now an assault weapon? What about a hammer, or a baseball bat? The issue is that when definitions are not clearly defined, the government can use the broad definitions to change the intentions of laws.

Assault Riffles, because of they are defined, are already heavily regulated and illegal. So when people say they want to ban “Assault Weapons”, they can’t be talking about the already illegal and regulated Assault Riffles.