As a legal matter, this may be a Free Speech case.

As a legal matter, this may be a Free Speech case. However, having read what the individual concerned posted to FB, it is identifiably abusive, violent, threatening, and dangerous. I think treatment and evaluation should be required, in a locked facility as needed until deemed non-threatening. If you were simply incarcerated without that, then perhaps the approach to sentencing in this case needs to be addressed.

I don't think we should lock people up just for being stupid. Nonetheless, "It's a rap song" is the worst man-splaining I have ever heard. No. You were/are depressed and angry and you wanted to hurt your wife. You had specific and detailed descriptions for doing so. You threatened others. I am sorry you did not have someone in your life who said, "Whoa, dude. You need help. I am taking you to a minister/ counselor/ social worker/ doctor. NOW." Stating you would never really kill your wife is just part of the pathology, even if you lack that insight right now.

If someone wrote snail mail with this stuff, it wouldn't be a question. The internet is not fantasy land with a free pass on uncontrolled behavior. It's real and it's part of the real world and people need to start acting like it.

http://www.cnn.com/2014/12/01/politics/supreme-court-elonis-vs-u-s-free-speech/
http://www.cnn.com/2014/12/01/politics/supreme-court-elonis-vs-u-s-free-speech