Katie Porter was exposed for berating a staffer and throwing a tantrum during an interview in two video clips this week.   And the California governor candidate is even worse when cameras aren’t rolling, one ex-staffer told The Post Friday. One of the lawyer and politician’s cruelest tactics is dehumanizing her young underlings by referring to them in the third person — while in their presence. “It was easier for her to do these things to the quieter ones, the more soft-spoken ones, who wouldn’