While I personally like the poster very much, I think its use could backfire if it were placed in locations where the non-shooting public could see it.
Recall the thread here recently where a non-shooter found a 22LR cartridge in his garden, came unglued, and posted a photo of the cartridge to a board that he frequents. The other posters, also not shooters, thought that this was an extremely dangerous situation.
Point being, the general public has no idea what an assault weapon is, and if Dianne Feinstein tell them that a Springfield is one, well, she's the senator. I could easily picture a non-shooter saying "Good God! You mean *that* rifle isn't banned, too?!?!"
Tim