No, they get arrested for conduct that would be criminal no matter where they did it. Facebook (2x) and Twitter (2x) were the (virtual) venues where the crimes were committed, but the crimes were attempting to organize a mob to burn down a courthouse, inciting and threatening to murder police, conspiracy to suppress votes and threatening to kill the President. The crimes would be just as criminal had they been done in person at a local bar (or any other physical location).