Sometimes it can help to understand where the person is coming from, why they have formed the impression that they have. It doesn't mean that they are right about the claims. But it can make it less frustrating to listen to them, and may provide an opportunity for gently nudging them in a better direction, or educating them as to a more accurate picture of the situation.

Defensiveness is what John Gottman calls one of the 4 Horsemen of Relationships. Gottman studies couples in his lab, so his ideas about relationships are based on data. There is discussion of defensiveness in his books, and several posts on the Gottman Institute blog, such as this post http://www.gottmanblog.com/archives/2014/10/31/self-care-defensiveness?rq=self%20care

The other thing to look into is why it stings so much. If you can figure out why it bothers you more than more neutral topics, then you might be able to see past the things that are making it difficult to evaluate the claims.

It's also possible that all of the specific claims are not true, but that there is nevertheless a problem, just in a different area than the person who is making the claim thinks there is. There might be something else you could do that seems unrelated, but fixes whatever issue you are having, and adjusts your behavior enough that the person stops wanting to make those claims.