[tshaddox]

I'm not familiar with #KillAllMen, but it sounds rhetorical, and even if it's not, it doesn't appear to meet the US standard of "imminent lawless action." Speech can only be limited if the speaker intends for it to incite violence, and that the violence is both imminent and likely. You can literally intend to incite violence at some unspecified future time and that speech is protected. You can also just tweet out incitement for violence at a specific time and it's probably protected if you're a random person with no following or influence that is likely to cause the violence to actually happen.