***Minor spoils****
Well he watched his brother die. I think the situation is a bit different than what Jon has typically gone through. His emotions made him make a mistake. Jon does hold family close(He died and was tricked because he thought Benjen returned and almost left the nights watch when he had heard that Rob died), it is a little different from being honorable or trying to do the right thing in regards to the wildlings and such.
Even in the Finale preview he tells Sansa that she should trust him as they got enemies from all angles.
Also Ramsay is not like any type of foe Jon has had to face.
Jon hasn't made a complete 180, like Sansa almost appears to have(to more of an extent), He just lost a piece of himself when he died. Makes sense too. Each time Beric Dondarrion was brought back from the dead he said he lost a piece of himself.
I think that was evident went Jon confronted Ramsay in the Winterfell courtyard. The look in his eyes wasn't like him and he probably would of beat Ramsay to death if he never saw Sansa.