“Fighting oppression is more just than committing oppression” is a norm that has an incredibly long history. What also has an incredibly long history is trying to elevate the importance of the marginal consequences of those fights, over what was being fought against.

Because enslsavers created the situation in the first place. They wronged themselves by taking people who could have been educated and empowered and instead taught them violence and ignorance.

The same reason we don't get too hung up on American soldiers slaughtering SS officers after liberating concentration camps. Two parties can both be in the wrong while at the same time one is way more in the wrong.