Hmm, I'm also running 4.3.2 and it seems to be opening ok. Can you right click on it and try to select "open with XCode"? If that does not work try reviewing the file info using the "get info" option in finder.
If nothings comes out of that, try redownloading it, it sounds like something could have been corrupted on the download?
Let us know how it goes!
OK, by clicking directly on KitchensinkCordova.xcodeproj I was able to open the project, I must have been doing something wrong.