The Fences shell extension for the context menus are in:
C:\Program Files (x86)\Stardock\Fences\FencesMenu64.dll
Depending on if you have a 32-bit or 64-bit operating system. Unfortunately it's all or nothing in this case. As the actual strings themselves are contained in the DLLs, you will have to disable all Fences context menu entries. To do so, download ShellExView from here:
32-bit OS: http://www.nirsoft.net/utils/shexview.zip
64-bit OS: http://www.nirsoft.net/utils/shexview-x64.zip
This is a small standalone application that lets you see what shell extensions are plugged in. Run the program and scroll down to the' Extension Name' of 'FencesShlExt Class' and select it, then press 'F7', which disables the current selection. To re-enable at a later time, simply select it and press 'F8'.