I remember that one very well, too. I started yelling at the TV, "You've gotta be kidding me! That gun probably just saved your life! Or at least kept you from being beaten to a bloody pulp AGAIN!"
That show has had several anti-gun messages thrown in throughout. Unless you count the gun-toting lesbian doctor that was on the show briefly...
I stopped watching ER when sex became the major topic, was that first or second season? Now it's FNC, documentries and old syndications.