First, this is your judgement as a person sitting comfortably in front of a screen. In the last episode of season 2 everything has been happening in the heat of the moment. Walker was under such pressure that he has been unable to keep a level head and for the same reason Francis has been extremely desperate.
Second, as an ambitious man he was, Walker wanted to get the situation under control on his own. He didn't just want to use Frank. He was also a good man and wanted to forgive Francis after all, he didn't want to falsely sacrifice Frank just to save himself. Francis knew that, and he deceitfully showed humility so that he could re-establish a dialogue with Walker.