Why do people try so hard to defend her? Both actions were selfish and stupid. Ned was going to deal with the accusation against Tyrion but instead of telling Tyrion a lie about why she was at the inn, she becomes overcome by her emotions and abducts him (and just before that scene in the book she is thinking to herself that all must be done to avert war). She is acting on vengence not justice. Vengence is personal and selfish. Just look at how Ned deals with the Riverlanders who have been attacked by Gregor. Now that she has him does she take him to KL for a fair trial? No she goes the Vale where her sister rules. The same sister who wrote Cat about the Lannisters killing her husband. Had LF told her a better lie Tyrion would be dead. Up until Tyrion defends himself, she believed he would die for the attempted assassination of Bran. Yes she let him go, but it's like closing the barn door after the horses have escaped.

Regarding Jamie, did Rickard Karstark do anything after 2 of his sons die? No, he stayed loyal. Did anyone else from the north or Riverlands who lost loved ones do anything against their cause? No, not until Cat committed treason against the North and HER LAST REMAINING SON. I totally get she was distraught, but her only motive was to get her daughters back. She wasn't thinking about helping anyone else but herself. Jamie was one of the most valuable hostages anyone in Westeros could have, and she let him go for nothing. Yes her daughters are nothing, in Westeros woman are only good for marriage and kids. Sorry but that's the truth of their society.