Just off the top of my head, it sounds like these were specific threats of bodily harm, which are not protected as free speech. You can threaten someone with eternal damnation, since presumably you would have no real influence on such a thing (if there even IS such a thing), but you can't threaten to "take them out". Those anti-gay protesters from the WBC do NOT threaten physical violence, only spiritual condemnation. Most pro-life protesters do the same, not actually attacking or threatening their targets. Those who DO cross that line are investigated and, if needed, arrested.