Well... Im sorry that you feel like you have to threaten me because Im complying with the terms of your contact and I'll be sure to return the favor when I get your rental verification...
Let them write the review, come back with a professional, to the point, great reply making them look like they may have not read their lease properly and you'd love to assist them with going over it again so there are no misunderstandings.
Of course....but you just do your job, assess the charges, and try to diffuse..."...sorry you feel this way, you will have to do what makes you happy..." - and so on. "We inspected your apartment before you moved out so you had the opportunity to rectify."