Greene is very careful to build up the character of T. as being a boy who is dangerously disconnected from any emotions whatsoever. The experience of being brought up during war and its aftermath has had a very worrying impact on T., as this quote and others in this brilliant short story suggests. His fascination with destruction and his desire to enact a complete dismantling of Old Misery's house is something that Blackie interprets as having to do with some kind of human emotion. Yet T.'s response as highlighted by you only serves to emphasise his comple inability to experience "normal" human emotions. Consider what T. goes on to say to Blackie when burning Old Misery's life savings:
The last burning note illuminated his brooding face. ‘All this hate and love,’ he said, ‘it’s soft, it’s hooey. There’s only things, Blackie,’ and he looked round the room crowded with the unfamiliar shadows of half things, broken things, former things.
The quote you highlight shows the truth of just how T. is completely detached from normal human emotions and experience. He knows nothing of love or hate.