Young people tearing down posters of Israeli hostages and launching waves of anti-Israel demonstrations say they’re being fueled by thousands of pro-Palestinian videos, mainly on TikTok and Instagram. Ripping down posters and lavishing praise on those who do has become a trend ever since Hamas terrorists took 240 Israelis hostage during their Oct. 7 terror assault on Israel. More than a dozen protesters interviewed by The Post in Manhattan said their opinions about the Israel-Hamas war was shaped mainly by Instagram and TikTok accounts — and to a lesser extent their school professors. They were at a rally on Thursday...