And how is the doctor/scientist that works for the Governor still alive? He is straight up stupid. Keep playing your crappy records, its not gonna help you.
Garth
Being intelligent is more than having an omnipotent understanding of the world around you. While we understand many of his 'experiments' are likely flawed - we only do so because we've been told as much by the omnipotent narrator/story editor. There's no reason to expect anyone to know that the virus takes over the primal part of the brain removing the past self entirely. The experiment he created was the best you can do without access to any kind of medical equipment. That he is thinking about the virus singles him out among
everyone else we've met so far except the one scientist at the cdc who was studying it. He stands out as a thinking man among survivors, someone who takes the scientific approach and considers important elements of a survival situation like stock supplies and energy demands.
That he hoped and wanted to let the old man be unrestrained doesn't make him stupid - it makes him niave and human. He hasn't seen the narration we have, and he's never seen anyone turn. He knows the dangers, he just hasn't seen enough evidence to fully explain them in a way that would modify his actions to be more like the people around him.
He may not have experienced much of the outside worlds required brutality in his survival of the apocalypse. We have no idea how long he's been at woodbury. He may have lived in an apartment near it and managed to stay in civilization more or less continuously. You can't expect someone with that experience to react the same, or to have the same life view as someone whose had to hunt and forage in zombie infested territory for an entire winter.
Michonne is a character that I just don't get. She is awesome as far as the sword wielding zombie killer, she is just inconsistant. I mean she will kill her pet walkers with no thought, she will kill a crazy old man in his cabin like it's her job but then she has had chances to kill both Merle and the Governor and has not done it.
Garth
The conditions of those four incidents makes her actions very consistent and well thought out. The pet walkers were killed to keep them quite to evade capture, and it was done in a controlled situation (only andrea watching). The old man in the cabin was done to keep him from unleashing a horde of zombies into a confined space and it was among people she mostly trusted at that point (seen through multiple shots of her overhearing their group dynamics and smiling or thinking), it also put her in the position within that group as someone to respect and not roll over.
With the governor she was in an enemy encampment surrounded by gun weilding people willing to mercilessly kill innocent outsiders at the governors command. Had she slit his throught she would have had to fight her way out of that alone. With merle she did her best in close quarters but there are limits to what you can do in a fight. She's strong and capable but he had a gun and there were walkers present - there comes a point where escape, evade and ambush is the best available option. Standing her ground and going toe to toe with him is a brash gamble, if survival is your goal those kinds of gambles aren't pretty options. When she met him again in town there were two people there that she didn't know and she was already wounded - and most importantly
at a distance against 3 potential opponents all wielding guns. To hobble into that fight would have been suicide.
Machonne protects herself. When she trust someone, she does her best to protect them, until they put her in a place of danger. Then she has to protect herself first. That's been pretty consistent so far.