A person in Texas posts on the internet angry denunciations of a man in California, posts his address and the names of his wife and children, and encourages physical attacks on their persons and property. Can the man sue the person from Texas in California?
The answer is yes, but the lawsuit has to be done correctly. In this particular case, the California man tried to handle the lawsuit himself, made too many mistakes, and will have to pursue any further legal action in Texas, which he is doing.
The general rule is that: "A nonresident defendant may be subject to the court's specific jurisdiction if three requirements are met: (1) the defendant has purposefully availed itself of forum benefits with respect to the matter in controversy; (2) the controversy is related to or arises out of the defendant's contacts with the forum; and (3) the exercise of jurisdiction would be reasonable and comports with fair play and substantial justice."
Just posting something up on a social media site or other publicly available website is not enough. That's not availing of the target state's benefits or arising from contact by the bad guy with the target state. Instead, the victim must show that the bad guy expressly aimed and targeted the message to California.
Jurisdiction was allowed in a case against a Florida newspaper with a circulation over 600,000 in California, where it published a defamatory article about a person in California, based on interviews in California, and which damaged her professional reputation and income in California.
Jurisdiction was not allowed in cases where a false advertisement was posted on the internet generally, not specifically targeting California residents, and where an article was posted on the internet generally which falsely damaged the reputation and income of a California company.
Posting a family's names and home address, and advocating physical harm to them should be sufficiently specific aiming and targeting at California to allow a California court to step in. However, the procedures imposed by law for how evidence is presented are for the protection of all of us, by establishing "due process." For example, written testimony is required to state that it is made "under penalty of perjury," so that the witness will be in jeopardy of prosecution if she or he lies. This plaintiff representing himself failed to do so. As a result, there was no admissible evidence of hate-speech aimed and targeted at California.
If you or your company has been falsely accused on the internet, the courts may have a remedy available, but if the speaker is out-of-state, there will be some extra technical hurdles to the case, and you'll need a knowledgeable attorney.