Well if someone is going to harass someone else, they should do it openly with their own name. They shouldn't hide behind anonymity (except in cases where they'd be put in physical harm if their identity was known). With that said, Yahoo should not have to surrender client records if it doesn't want to. The court should not have the authority to compel Yahoo to surrender data when Yahoo has not committed any crime.
I am just mildly entertained that he went to that much effort. If someone was harassing me in e-mail, and I wasn't in 7th grade trying to keep my reputation unscathed through puberty, I would probably just block them. Or ignore them. This looks more like tit-for-tat, he apparently wants to one-up somebody and make whoever is sending these e-mails pay to litigate over it. And then he posts it on his news page, you know, like it's news, where further down the page he ironically makes himself out to be the champion against the "frivolous" actions of other lawyers. I guess he has plenty of time on his hands, not a whole lot of clients I guess, perhaps New York's divorce rate plummeted to zero ever since they started accepting gay marriage and there's just not a lot of business anymore.