That was not the only threat they received. I don't know why articles choose that statement but every one I read said "statements like..." were received.
But also the article state that they did not get security UNTIL pictures of their homes were posted. So it wasn't the threats that prompted hiring private security. It was the fact people were finding out where they live and posting their homes and addresses to the public. THAT is likely what was deemed a threat. The articles state that they received threats and online harassment.
I got charged with felony witness intimidation (basically harassment on steroids) for telling someone falsely accusing me of a crime they 'were a piece of crap, and needed to die and go to hell". Just my two cents.
What a threat is, and how it is defined is a matter of law. Some threats when conveyed via the internet may not be a crime, though the same threat conveyed in person and coupled with the apparent ability and willingness to carry it out may be. Without knowing the exact "threat," the means conveyed, and how serious the intended victim might have considered it, it is impossible to say.
You can Google the terms for Washington state and find out what it has to say about threatening communications and the like.
It turned out that the charges that I was upset about my accuser lying about were dropped by prosecution almost immediately on basis of "complete lack of direct evidence." According to my lawyer and the state statutes on witness intimidation, the prosecutors had no choice but to eliminate the felony charge and replace it with lesser misdemeanor "malicious use of a telephone..." one of the goofiest charges I have ever heard of, but it is what it is. So on that basis, yes in Michigan you can actually be charged with being mean to someone but you have to do it with a telecommunications device.
It's not just Michigan. There are a great number of states where threats, harassment, etc. can be accomplished via electronic communications (text, email, messenger, ad nauseum). Bottom line is, don't threaten or harass people. :-)
That's kind of a threat more so than "I hope you get cancer." But no one in the OP story was charged with a crime of harassment. The Price Waterhouse attorneys FELT the need to hire PRIVATE security because of what people were saying and then posting photos of their homes online. They didn't seem to file any reports of threats or harassment. They just hired private security. I don't see why that's a big deal. Anyone can hire private security if someone says anything to them. There's no law against hiring your own security to protect you.