Kfir Sharar didn't know Tali Hatuel and her four young children, but their murder by a terrorist in May in the Gaza Strip spurred the 25-year-old economics student into action. As a secular, fun-loving Israeli, Sharar admits that he doesn't exactly fit the stereotype of an activist. Sitting near Jerusalem's Central Bus Station, with sunglasses hanging from his half-opened button-down black shirt, Sharar said he would rather be out dancing or telling a woman he loves her than getting ready to stand in the human chain that ran from Gush Katif to the Western Wall on Sunday. But it would...