What kinda logic is that? (Spoilers)

John Agar's character murders his mind-controlled wife, then spares the man directly responsible for her falling under control?

First off, he assumed all too quickly that there was no way to free her. Try killing Zontar. Try plucking that thing out of the back of her neck. Second, if he was going to go to the extreme and kill his wife, there's no reason to believe he would spare his best friend. He seemed to love his friend more than his wife.