Did you do much else besides install Sabayon 9 kde? If not, it would probably be easiest to reinstall from a different DVD to get you where you want to be.
This question gets asked multiple times, I think it's time for somebody to create a wiki page about it, because I can never recall the answer perfectly.
The short answer is, you can't remove all components easily. Removing a meta package doesn't (and never has) remove all the packages. kde-meta is a shell package with lots of dependencies. Instead of removing that, you want to find a base package (one that lots of kde-stuff is dependent on) and remove it and everything that depends on it, perhaps something like kde-base/kdelibs
Note that removing kde-base/kdelibs will remove tons and tons of stuff, possibly more than you even want removed, unless you are absolutely sure you want every bit of KDE removed. Make sure you run the remove command with --ask and check the package list before proceeding. Removing too much might leave your system usable.
That said, unless you are running out of hard drive space or have limited bandwidth for updates, there is no real harm in having kde installed. If you don't use it, it won't hinder performance.