There's an odd theory in history that you become your enemy.
Over time, whatever group or cause you focus on, you demonize it so much, justify fighting them the same way they fight you (or you perceive them to be fighting you), that eventually you're just like your enemy, only with different slogans.
That's why political differences should never be represented as wars, and groups of people with other opinions as enemies. Every effort should be made to personalize people who disagree with you, humanize them, show them kindness they do not deserve (at least in your own mind). It's not for them; it's for you.
Wars are bad not because there's some worthy cause that we confront and eventually defeat it, making the world a better place. Wars are bad because they harm the people fighting them, many times forever.
In the free world, we've realized that peaceful, loving, kind civil disobedience is the only way to change ourselves for the better. This is why. It has nothing to do with how worthy our cause is or what an awful thing we're defeating. It's about the stage we leave for the next generation with their struggles.