There's an easy fix: http://wiki.inkscape.org/wiki/index.php/FAQ#Copying_and_pas...

damncabbage · on Feb 19, 2012

Note:

  However, this will also prevent copying text from any
  X11 application to Mac OS X ones. It will not prevent
  copying text from OS X to X11.

But:

  When you just want to make a copy of an object within
  Inkscape, you should use duplicate (Ctrl-D) rather than
  copy/paste (Ctrl-C/Ctrl-V). Duplicate does not interact
  with the X11/OSX clipboards.