What kind of dog is Pitbull?
"Pitbull" is a common name for a type of dog that was crossbred from bulldogs and terriers. Originating in England, they were historically used as fighting dogs for blood sports like bear-baiting and bull-baiting. They are also commonly used in illegal dog fighting rings in the United States today. For these reasons, many people discriminate against pitbulls despite the fact that studies show they are patient, friendly, and not any more aggressive than other dog breeds, like golden retrievers. Tom Holland is likely referring to this history. He is expressing that it is ironic that pitbulls are illegal in the UK, despite the fact that they originate from there.