It's rude to ignore someone after kissing them.
Carl went out with Krista and kissed her good night at the end.
Carl wants to break things off with Krista because he didn't enjoy their time together.
Carl lets Krista down gently and tells her that he doesn't see them working out together.
Carl blocks Krista's number and ignores her.
Krista is upset but understands.
Krista worries about Carl and feels hurt that he is dumping her without explanation since she thought the night went well.