This seems like the type of short sighted comment you'd see at someone buying a copy of the Communist Manifesto. "How dare you exist in capitalism while also being critical of it"
Sorry, they didn’t buy food or even just some random thing to bring them enjoy… they specifically bought a shirt to criticize capitalism. That’s about as ironic as you can get. It’s not just “existing in capitalism”
Edit: now if it’s a self-referential ironic joke of a shirt… bravo, love it.