Reminds me of when princess Diana died because her driver was supposedly drinking and driving. My parents were talking about it, and all I remember thinking was that her driver was drinking a cup of coffee and spilled it on himself, resulting in a crash.
In the Tolkien universe Orcs are objectively evil by design. They were warped from elves and all of the traits that we would call good were removed.
They aren't capable of any kind of morality, compassion, kindness or decency on a spiritual and biological level
As such while its nasty business using your curse to defeat them by their own means doing so that people who are capable of decency can live and thrive is a moral act