It seemed to me that he came pretty close to calling for insurrection. Whether this comes under free speech strikes me as questionable, but whether or not there is a legal issue, I think it is highly irresponsible for an elected official to speak favorably of insurrection.
On the other hand, we have elected officials in states like Ohio presiding over elections and clearly working to disenfranchise citizens who might vote for the opposition. That strikes me as grounds to federalize the election, but that would really be chaos!