Call me a simpleton, but I don't understand the connection between packing heat and health care. I've been to a lot of protests in my life -- anti-war, anti-corporate globalization, anti-xenophobia, pro-peace, pro-equal rights, etc. -- but I've never even thought it necessary to carry a gat, nor would I have seen a connection between any of these causes and my right to bear arms.
I suppose if you go back to the 1960's with the Black Panther Party for Self Defense you have the same sorts of images, but even in that case there are few parallels; after all, the Panthers were calling attention to the lack of protection they were getting from the government and the need for self-defense. They weren't protesting health care; in fact, they were often providing social welfare services.
The similarity in both cases, I suppose, is that the gun functions as a prop, a bit of costume. In the Panthers' case, it was to promote an image of strength and self-reliance in the face of nearly 400 years of racist oppression that at the moment seemed particularly virulent, what with assassinations of prominent Black figures and the mass murder of less-prominent blacks.
So in this more recent case, what's the prop represent?