Which leftwing blockhead said that? That's like saying freedom of the press only applied to printing presses and only to those of the type available in the 18th century.
IIRC, the leftwing blockhead (good term!) who said 2A was only about flintlocks was CJ Warren Burger. He appeared on the cover of Parade magazine grinning while holding a 1795 musket and in the feature story said basically, screw you NRA, this is what a strict interpretation of 2A allows you to have, so STFU!