Okay let‘s talk about this for a second.
Let’s talk about how he’s going at it with Lysa. How hard he kissses her, how he devours her, how he just completely shuts her up and takes her breath away, how he just takes her right then and there, almost mercilessly, how he shows her that he is the one who makes the rules, he is the one who demands, and all she has to do is bend her will to his, give herself to him, completely, absolutely, and it’s so sweet…
And then let’s talk about how he’s kissing Sansa, so carefully, gently, respectfully. He doesn’t demand, he doesn’t take, he asks, he offers, showing her that she can make the rules, she can set the pace, and he will follow her willingly. Because he is feeling things for Sansa he doesn’t feel for Lysa, and it’s not just lust and passion and, maybe, the memory of Cat.
What he’s feeling for her is respect. He doesn’t want to frighten her or confuse her, he doesn’t want to overwhelm her, but he can’t not kiss her at that moment. He can’t resist the beautiful snow maid. So he kisses her gently, and when she turns away, he respects her and immediately lets her go.
This kiss, maybe more than her flowering, more than her marriage to Tyrion, showed Sansa that she is a woman now. And Petyr sees her as that. He sees her as a grown woman, not some frightened child who doesn’t know any better and who he can take advantage of. Sansa is strong, she is a force to be reckoned with, at least she will be under Petyr’s counsil. And with that kiss, he has shown her all that. He hasn’t just offered her his body, he has offered her his mind. He has shown her that he sees her as a woman who might as well become his equal one day.
Petyr’s marriage to Lysa was short, fast, ruthless. He took what he could and when she was of no more use, discarded Lysa.
Petyr’s relationship to Sansa is different. It’s slow, careful, deep. He’s in it for the long haul. He doesn’t want to take, he wants to give. And he showed her all that with a single kiss.
Just a reminder that I am clearly talking about book!Petyr because there is absolutely NO EXCUSE for what show!Petyr did in season 5.