Right.. all those weren't his fault.
He didn't make t-bag stab the guard, he told him not too.
The cat died from Bellick.
Sarah killed herself (Well she may not be dead).
Westmoreland got himself killed through the fight with Bellick (through accident of course).
Also, Michael wasn't planning for anyone to die. Even so, what was he supposed to do when someone died? Take responsibility and watch his brother die? The deaths weren't on his hands.