See that's the problem. Like a week before that Walt killed 2 people just to save Jesse's life while not gaining anything and losing most. Then he bargained for Jesse's life with Gus. Then he was hiding Jesse from Gus for all this time. He didn't want Jesse to kill Gale, he wanted to do it himself but when Mike arrived to take Walt down the only thing left to do was for Jesse to kill him. It was either he does that or Walt dies, it was the last thing he could do. It wasn't a play, it was a desperate attempt.
I also don't like how quickly Jesse starts to idolise Mike and Gus, people who would have killed him 2 times if not for Walt.