I have the same issue with audiobooks, some podcasts and even some ring tones that relentlessly appear within the Music folder no matter what you do.
I did discover that switching iTunes Match to 'off' would make the previously grayed-out Media Kind option re appear for changing (although note: there's strangly no Ringtone option here). This then enabled iTunes to automatically re-locate the Media Kind to it's correct location when selected within options. Problem is that I've paid for iTunes Match and would prefere if it was not disabled but as you may be aware, is that when re-enabling iTunes Match the problem re-appears again.
I have read Matt Miller3's solution and will no doubt have to perform that task as a fix (thanks Matt Miller3). But I'm left wondering on a couple of issues; firstly, is iTunes Match incapable of auto-refreshing changed and edited information & attributes to the referenced and stored information within the cloud? (I am shocked), secondly, if dragging all those files/audio books in question out of iTunes (with Match disabled), then deleting within iTunes before finally draging back into iTunes and setting the correct Medi Kind in Options before re-enabling Match, does any re-compression take place when dragging out of and then back into iTunes resulting in a slighlty lesser quality that before?
Mmmm.... as a side note iTunes Match does have some surprises and I was caught out with many higher quality lossles files not being matched even though they're probably the most widely available albums in history which I had manually added from my CD albums (Bad, Dangerous,Blood on the Dance Floor, etc). I would have thought that Match at the very least would run a kind of Shazam short listening test regardles of stored song quality type and then match and make available in the cloud as Apple's iTunes Plus only quality - this would have been more than acceptable.