Well, here's some more from Lewis, as interpreted by me. But any piece of writing can be read as "a set of bare, unsupported assertions", as the tortoise said to Achilles. The reader always has to work out for himself how the things fit together to make a machine that goes, especially with an isolated quote.

The quote is from an essay called "The Humanitarian Theory of Punishment". (You can google up the full text.) The eponymous theory, which he opposes, is that the sole functions of punishment are deterrence and reform. This implies (he says) that the sole standard by which to judge the laws prescribing punishments for crimes is the matter of fact: whether those aims are achieved. Are potential criminals deterred, and are actual criminals reformed. Justice is irrelevant. There is no such thing as justice, only welfare, collectively assessed. This implies the view of people expressed in the quote: to treat them no better than children, animals, or imbeciles. No individual matters to the advocate of this view, any more than a single cow matters to a farmer, who will slaughter it at once if it has picked up an infectious disease. The good of society as a whole is all that matters to this sort of humanitarian; which means, as Lewis is not the only one to observe, the good of the people on top, the would-be tyrants for whom, as I remark in another comment on this thread, a view of how people should live is necessarily a view about how people should be made to live.