And that is 100% constitutionally protected speech. A broad-based call for revolution, even violent revolution, is not the same as a specific threat to an individual(s). In addition, overthrow” can mean change via violence, for sure, but it can also and very legitimately just mean changing the system of power by any number of means. You can “overthrow” a governing system/apparatus via elections, via protests, via incremental reform, via constitutional changes, and yes, via violence.