Calling modern rifles assault weapons?
To call these a weapon of war is misleading and absurd. The rifles used by US troops are much more sophisticated and lethal. They also can be switched to fully automatic firing. You are unlikely to see troops using an AR-15 in battle. While some of these rifles look like the M-16 version that was introduced in Vietnam there are still significant differences despite a similar appearance.
I think the left calls these weapons "assault rifles" because they look scary to them even though their operation is not materially different from other semi-automatic rifles.