BERLIN (Reuters) - Berlin Zoo rallied to the defense of Knut, a three-month-old polar bear cub, Tuesday, rejecting demands that the animal be allowed to die after being abandoned by its mother. The fate of "cuddly Knut" has gripped the German capital since his birth in December. Rejected by his mother Tosca, the cub was adopted by a zookeeper who moved into the animal's enclosure to care for him round the clock. Some animal rights campaigners think this will humanize the bear too much and want the zoo to stop saving young animals. "Hand-rearing a polar bear is not appropriate...