Oh, wow, that's horrible that this neighbor is acting so vile, I apologize, not all New Yorkers are like that, and I say that because I live in New York. If I hadn't broken my outdoor surveillance camera I would send it to you to set up and use. Well, if they do call and leave a message on your husband's cell, do not erase it. It may also be a good idea to not answer if he/she calls back and jsut play a game of phone tag so you can have everything recorded. It may be illegal to record a phone call, but it's not illegal to save the voice mails and use them for your own safety, which is what this sounds like to me.
Also, I forgot, please print out and save those posts that they made - document everything