Can you boycott a store if you've never shopped there in the first place?

I am extremely annoyed with a Haight-Ashbury boutique that (apparently) bans babies and children from entering the premises. The boutique has a note near the door that says NO BRATS with a picture of a weeping child. (huh? weren't the store's owners and employees children at some point in their lives? and did they never cry?) The problem is this; the store sells ugly knicknacks and clothes, and so I've never shopped there in the first place. Is it possible to boycott a store when you don't shop there anyhow?

I'm thinking of going in there, buying a couple of items and never shopping there again. That'll show them!