Brisbane, Australia CNN  —  Kirra Pendergast talks to thousands of teenagers each year in her role as a cyber safety educator. She knows what they get up to online – the texting, the bullying, the sextortion, the threats – but nothing prepared her for the hostility she faced this month in a roomful of students ages 12 and 13. She’d been booked to give three talks at a high school in Australia but just minutes into the first session, a group of boys started shouting insults common among