Typically, the speech of a sitting US president is given an incredibly wide berth, being regarded as immune from being sued over their official actions - a defense Trump has invoked over his comments on January 6. However, the lawsuit was filed under a Reconstruction-era statute in response to the rise of the Ku Klux Klan, a white supremacist terrorist group, that specifically allows for damages when force, threats, or intimidation were used to prevent government officials from carrying out their duties.
“Just as denying First Amendment protection to incitement does not unduly chill speech in general, denying absolute immunity to incitement of imminent private violence should not unduly chill the president in the performance of his traditional function of speaking to the public on matters of public concern,” the attorneys wrote.