War. War never changes. Oh, wait, that's Fallout, not Star Wars.
But the point is that there are casualties in war, sometimes those casualties are innocent bystanders. Well, that and without knowing very specific details such as how much of the death star's debris would have stayed in Endor's gravity well, what the mass of the death star was, what materials were used etc..
A significant amount of debris did not end up on Endor, depending on many factors, most of the debris could have landed in an ocean on the other side of the planet. Or maybe the little cannibalistic teddy bears all died horrifically.
That doesn't make the Rebel Alliance's actions evil, it just means there is always collateral damage in wartime.