He practically leaves and cheats on Asami and just kicks her to the curb for for Korra. I mean, obviously Asami's still going to have feelings for him, so when he breaks up with Korra...he's still continuing to flirt with her and kiss her.
Don't get me wrong, Asami is still a little wrong in the situation. I understand he was her boyfriend first and didn't go through a proper breakup, but she's gotta get her head out of the clouds and realize what she's doing or Korra will just have to go into the avatar state and kill both of them.