The moment you decide that horrific violence is okay if it's aimed at Bad Guys™, you immediately have an incentive to categorize all of your "enemies" as Bad Guys™ in order to justify violence to them. They are not people anymore, they aren't complex and diverse human beings with their own motivations and lives and desires, they are the Bad Guys™ and everything done to them (no matter how horrific or indefensible in any other situation) is okay because it's for a Good Cause™.
The only way to not fall into that sort of mindset is to just not let yourself create exceptions for your basic morals. And that isn't EASY, you have to correct yourself constantly and break away from people and blogs and new sources and the like that push dehumanizing and violent narratives, but it's the only way to approach sensitive and important topics with kindness and compassion rather than hate and anger.