Like everything else, it depends. In the extreme case, if you eat beef every day but use a bicycle for transportation, live in a mild climate with little need for heating and cooling, and rarely fly in an airplane, your diet could be a significant part of your carbon footprint in percentage terms.
Eh, it's just that the entire supply chain that keeps them alive means that their per-capita carbon footprint is almost certainly not dominated by their diet, let alone by beef alone (it's an outsized fraction, but it's just not that significant compared to other stuff). But yeah, hard to talk accurately in broad strokes about a very varied audience.
In this case, they said they live in Rome. Concrete, heavy machinery to make it livable, trash movement, maintaining their public transit, household goods, electricity via nat gas, etc. Sounds like they're making a good effort, though, and in terms of just the discretionary part, they might be right.
