Any time you stop looking at evil as a black and white thing, it's helpful. So the fact that there won't be any obligatory Islamic terrorist stereotypes in movies any more, that'd be helpful.
Ships are obliged to take on harbor or river pilots - who provide specialized local navigation - when they approach a port, but in the canal, a Suez crew is also obligatory. The crew members are there in case the ship needs to be moored during the canal transit, but this rarely happens.
Every judgement of conscience, be it right or wrong, be it about things evil in themselves or morally indifferent, is obligatory, in such wise that he who acts against his conscience always sins.
Summer is not obligatory. We can start an infernally hard jigsaw puzzle in June with the knowledge that, if there are enough rainy days, we may just finish it by Labor Day, but if not, there's no harm, no penalty. We may have better things to do.
We are all happy when U.S. soldiers are killed week in and week out. The killing of U.S. soldiers in Iraq is legitimate and obligatory.