Wouldn't it be legal to butcher feral rats in front of PETA HQ in each state? They are vermin, right? I would guess breaking their necks with traps would be legal, at least.
If that were a problem, bring a bunch of cockroaches and stomp on them in front of their offices.
I say get them as riled as they do the rest of us.
Either a bill was just signed, or waiting to be signed in CA that would give a dog owner 3 years in jail if their dogs killed an animal. Traditionally, dogs kill vermin.
So if you want to make a statement with butchering a rat, ensure you are in a red state.