A dummy is also called a pacifier in some parts of the world. Spitting the dummy is Australian for when a person acts like a baby with an outburst of over the top anger.
MUSE: I keep seeing politicians. Babies that sit in high chairs.
TANNILLE: On their golden thrones. Throwing tantrums. Spitting the dummy.
MUSE: Surrounded by the shi- crap they create.
TANNILLE: It does get up my nose, like a bad smell that lingers.
MUSE: No, that would be us the peasants darling. The byproduct of their greed. The scum.
TANNILLE: Ok, but could they at least be more discreet?
MUSE: It’s too late, they’ve started soiling themselves.
TANNILLE: Time for a nappy change.
MUSE: I hate to imagine the rash. I doubt they can be silenced.
TANNILLE: Bring out the dummy…