So from Kara's point of view, you're getting just as emotional and defensive about, and ignoring clearly articulated, rational, objective arguments for, the decision as you claim she is. Which is the point of the article - if someone goes into a discussion assuming they are the only one who is "objectively correct", they've already failed.
I've used the method outlined in the article very often in my career and it almost always works. Often it turns out I was right and we shouldn't have done X - but sometimes it turns out that Kara knew something I didn't, and X worked out way better than I expected.
Kara’s manager can encourage her to work on this, but colleagues cannot realistically. And even the manager’s ability here is extremely limited.