I stand by my position on the quote, however much additional of Disraeli that you may include. To say that Christianity is completed Judaism is to say that Judaism is incomplete. To say that Judaism is incomplete is to say that it is inferior to Christianity, that is lower in station or importance. To belittle is to portray something as less important. And that is exactly what Disraeli was attempting to do. He was saying that Judaism laid the groundwork, but that Christianity is the full flowering of G-d's message, and effectively that Judaism is missing the rest, is incomplete, and inferior.