Five black teen girls, convicted of a notorious Brooklyn hate crime, were spared jail after the mothers of the six white beating victims urged compassion for the culprits - citing the teachings of Nelson Mandela, The Post has learned. The forgiving moms wrote a touching letter to Family Court Judge Stewart Weinstein, asking him to reduce the sentence for the five convicted of assaulting their daughters in Marine Park. "Education is the most powerful weapon which you can use to change the world," the mothers wrote, quoting the African leader Mandela in the letter, dated Feb. 28. Instead of locking...