At the grocery store

I was in line ahead of two women who had been chatting quietly together. When the checker asked if I wanted paper or plastic, I replied, "Whichever is easier for you." He thanked me. He didn't have anyone there to help bag, and plastic was easier for him. I didn't care either way because I can both reuse and recycle plastic bags or paper bags.
As I was gathering up my purchases in their plastic bags to leave, the checker asked the women behind me, "Paper or plastic?" One of them immediately raised her voice to a louder-than-normal range and announced to pretty much everyone near the front of the store, "Oh paper, of course! We are very environmentally conscious!"
I still feel like punching her. Seriously. I think I need a punching bag at home so that whenever I come across people like that who deserve a good pummeling, I can imagine up their self-righteous beotch faces and get some good exercise out of it.
Argh!