One of the unfortunate effects of the age of social media is that people often say things behind the isolation of a keyboard that they likely never would say, in person, to the targets of their wrath. That doesn’t make violent threats over those media any less serious.

So, when Anthony D. Elonis of Lower Saucon Twp., Northampton County, threatened his estranged wife via Facebook, federal prosecutors did exactly the right thing in arresting him. Jurors later took his threats seriously and found him guilty of using interstate communications to make a threat against another person.

Among Mr. Elonis’ posts was this, directed at his estranged wife: “Fold up your PFA (protection from abuse order) and put it in your pocket. Is it thick enough to stop a bullet?”

Mr. Elonis contends he was experimenting with rap lyrics, joking with “Facebook” friends or otherwise venting.

The U.S. Supreme Court heard his appeal Monday, in a case that ultimately will set standards of personal responsibility for discourse over the Internet.

Holding Mr. Elonis accountable for his threats does not diminish his right to free speech. It simply applies to the Internet the well-established standard that rights come with responsibilities.