He did ruin his own life with his blinding stupidity, but that's no excuse for the State to compound that and ruin the lives of his partner and daughter as well.
Yes, he should have stopped to think, but 'Sticks and stones', and 'grow a pair' spring to mind as well. He might have (did) post horrible things, but he never intended to carry any of them out and never had the opportunity to do so. Those things have to be at the core of his sentence. Fine him: Yes. Make him do Community Service: Yes. Jail him: a big NO from me. Don't punish his daughter and partner.
Let me be clear. Cyber bullying is not acceptable and it has to be dealt with, but jailing people for using the language of the streets when online is not the answer. These are just words with nothing to back them up. If Nunn had made these "threats" and then travelled to the area the women lived with the intent of carrying his threats out; that would be different. He didn't, he didn't even know where they, the women, lived.