Well, maybe I should have said ancillary, or adjacent, or tangential, or something other than secondary.
Yes, Chapter 13 is The Great Love Chapter, but, in the context of the entire section, it's not THE main theme - the Corinthians' lack of God's kind of love for their fellow Christians may have been the #1 evidence they were carnal, and not spiritual, but the reason they didn't exhibit it was because they were coveting what they thought were the "best" gifts, and this led to a lack of love for others.
Hope I'm making sense here - I'm not trying to minimize the idea of God's love working in and through us, I'm just trying to show how messed up the Corinthians really were.
And, incidentally, if you take the Church in Corinth and overlay it over Christianity today, you'll find very little differences...