It's the standard cult apologists' explanation for what happens in any extreme situation, like Jonestown and Waco:  To blame everybody else in society for what happens except the person all the blame belongs to:  The Cult Leader, who in fact, is an outlaw. 

This is the rationale:  "It was Leo Ryan's and the Concerned Relatives fault that Jonestown happened, and that Ryan got killed on the airstrip, because by going to Jonestown, both caused an escalation of the cult leader's psychosis and actions.  Therefore, Ryan and the Concerned Relative should have known better, so everything bad that happened is their fault."

That's sort of like saying that it's a battered woman's fault if she gets killed, because she left her abusing husband and went to a shelter, and that's what caused the husband to escalate, killing her and all their kids, so therefore, it's the wife's fault she and her kids got killed, because it was her action that caused the escalation!!   It's true that a batterer might escalate when a wife leaves, but the blaming part, well, is totally fucked up logic.

I would define the spiral of deviant amplification as being totally fucked up logic, too.  Barker isn't the only one that spreads this nonsense around.