Font Book will not let you remove any fonts from the System folder. It will let you select them and choose Delete, but nothing will happen. Can't recall offhand if it does the same thing to the Library's Fonts folder. I don't use Font Bork.
There are many fonts supplied with OS X which do not need to be active all the time. See my article, Font Management in OS X.
I may receive some form of compensation, financial or otherwise, from my recommendation or link.