Because evil exists is not a reason to not confront evil.
America lied (either intentionally or unintentionally) about the reasons for invading Iraq post-9/11.
But that isn't to say that removing Saddam Hussein from power wasn't a global or regional good.
It's trendy and low-hanging fruit to bash the American military for international involvements, or its many failures.
But it's equally important to note that the times America has turned inward and taken a more isolationist stance have resulted in the greatest turns away from international diplomacy and transgressions of international human rights.
The alternative to "Team America World Police imperial global colonization authority with military bases all over the world like the friggin Roman Empire" is not "life as we know it, minus America."
It's every country is one dictator or military coup away from becoming an undemocratic state. So I'd weigh how happy a citizen of Myanmar or Venezuela are with their life vs the ugliness of American military power.