The behavior so far has not been targeted by legislation in the U.S. because of strong free speech protections.
I call BS on this. Free speech may protect the assholes from Westboro since they are on public property, but things done on the internet are done on privately owned sites. The trolls on Facebook that are mentioned in the article, are most likely violating TOS. Since there is no free speech on private property, laws could be passed even if they only involved civil penalties against the trolls.