Plus, so far as I know, the incidents you cite were all single nut job perps, while this one in NC seems to be organized by one political party and campaign against an opposing campaign.
Sirhan Sirhan was not a single nut job perp. Neither was the firebomber in this case. An organization, in RFK’s case the PLO, in this case the local DNC chapter, finds a single nut job, gets him worked up so that he’ll do the crime, and then the organization acts shocked and appalled, and denies any connection with the perp, who is in his glory since all the cameras are pointing at him, so he’ll keep mum about his inciters.