Ladies, thank you all for your advice, especially those who linked me to the renters' rights info. Amazingly enough, DH did NOT hit the roof, as I thought he would, and we've agreed to let the matter drop and move forward. DH is a big believer in karma, and the thought of the landlord getting a bit of his own medicine somewhere in the future was enough for him. I haven't decided whether to respond to the email I received, but I'm thinking that just ignoring him would be the best possible response at this point.
Thanks again. You guys are amazing!