[Heinleinian]

Presumably there's some kind of legal construct that could act as a poison pill. i.e. some kind of contract that says "if this patent is used for [insert evil purposes here], it is immediately converted to GPL."

Also, I refuse to lump defensive patent holders in with organizations like shell-corporation patent trolls or Intellectual Ventures. From what I can tell, IV isn't even bothering to try and execute on ideas they come up with. They simply brainstorm, apply for the patent based on the idea vapors, and then go after anyone who is putting in the blood and sweat to try and actually build it.