re first amendment
No, I think they were trying to say that sending messages using the email account of someone else is protected free speech. Which is equally the bullshit you're calling. He was free to send those messages, provided they were true, using his own account and the government did nothing to stop him from doing so.
The State on the other hand is saying using someone's email account without their permission is the same thing as pretending to be that person. And in this case you have to say they have a point. ID theft is not just about stealing money, it's the pretending to be the other person for malicious purposes part that's important.
I don't get why the guy killed himself, he could have got this person thrown in prison and cleared his name that way, so he must have been on the edge anyway.