To tell you the truth, I wouldn't mind if PETA kept their noses out of it. PETA is against fiskkeeping in general, not just inhumane fishkeeping practices. PETA aren't an organization that reflects any reasonable moral standpoint; they're an organization that actually believes animals to be of a higher moral worth than human beings. I dislike them, and I think the public in general dislikes them enough that if they were more vocal about these tiny betta containers, people might be inclined to side with the tiny bowl makers and the stores that sell them.
I think a much better approach is for aquarists who know what it takes in order for the fish we keep to thrive to take a stand against the marketing of such crappy devices.
Look at how much groups like the ASPCA and RSPCA have done to prevent the cruel treatment of other pets. Imagine how much could be done if organizations like these had a greater interest in preventing the cruel treatment of aquarium fish.