The second he saw he'd made the wrong assumption, Seamus opened his mouth to apologize. Until Percy said what he did.
Seamus's face went stony as his arms slowly came down to his sides. Percy was several inches taller than Seamus, but that didn't stop Seamus from invading his space to glare up at him. "One of 'those'? One of what exactly?" Whatever Percy said, he better pick his words very carefully.