At first, in my mind, I was defensive. Then I realized I was being petty and took the feedback to heart. In my response to the employer, I didn't try to change their mind, but simply thanked them for the feedback and moved on. After taking the feedback with a grain of salt, I realized that, while they weren't going to hire me, they had a genuine desire to see me land somewhere.

Sorry about your experience. I wish more employers gave feedback to unsuccessful candidates. Now I see why they usually don't.