I might as well add something else: The SDS was specifically mentioned to have been infiltrated by the Soviets, which likewise would include the KGB. If they truly avoided leftist causes like the plague to avoid indicating what their next move was, they wouldn’t even BE in the SDS, so that alone proves that claim to be false.
SDS was principally domestic. It was split into a Cultural Revolution branch which came to be Weatherman, a pro-Maoist group - the PLP and a community organizing branch - the Intercommunal Survival Committee.
There were more FBI agents there than KGB. Besides anyone associated with KGB would not be a trained assassin. Those would do everything to avoid ANY publicity.