That way, it can analyze human beings without having them increase entropy, which is something even the AI cannot undo.
But if you kill patterns that can be reused, you just waste entropy. So our argument is in favor of freezing, not killing.
Only if freezing expends less energy than killing. If it doesn't, the most energy efficient choice would be to scan humanity and then wipe them out before they use more energy.
A comment to http://singinst.org/blog/2010/10/27/presentation-by-joshua-foxcarl-shulman-at-ecap-2010-super-intelligence-does-not-imply-benevolence/: Given as in the naive reinforcement learning framework (and that can approximate some more complex notions of value) that the value is in the environment, you don't want to be too hasty with the environment lest you destroy a higher value you haven't yet discovered! So you especially wouldn't replace high complexity systems like humans with low entropy systems like computer chips, without first analyzing them.