If you read the piece OP linked (I highly recommend it, it is outstanding), or the whole book, the entire point is a warning about the looming threat of WW2, an

If you read the piece OP linked (I highly recommend it, it is outstanding), or the whole book, the entire point is a warning about the looming threat of WW2, and his idea of the 3 practical steps to keep the USA out of it. So he was indeed very much against the US involvement in WW2. That's the main point of the book.