Everyone complaining about ‘but reds!!’ should take a few seconds to think about diplomatic theory.
Given that we’re going to space, it is likely enough we’re going to meet aliens. I presume everyone can agree that we would all prefer this was a peaceful meeting that left everyone feeling like we can come to a further peaceful agreement. We already have enough working against us - space is big, but ultimately we’re all after the same space, and as history testifies that gets very bloody very fast even when everyone involved is the same species and knows each other.
If we come to the aliens with a record of ‘we let people commit and get away with mass murder’ this does not do good things for our chances. Think about it - if you were meeting a new person and trying to make a deal with them, would you feel good about it if you learned that they’d recently murdered one of their tenants and suffered no consequences for it?
And sure you can say 'but reds!’ - but whatever your theological opinions, the aliens won’t be living in our history. Reds look like other Amentans, talk like other Amentans, can pass for other Amentans on the internet, have been having their radio signals end up in space with everyone’s, have been present and a rather vital part of Amentan civilization for centuries. We don’t know enough about what the aliens are like. What if they had a pollution disaster they had to clean up from? Probably their pollution standards are different from ours. 'They’ll go right ahead and slaughter us all, as long as they can tell themselves we were polluted first’ is not a trust- or peace-inspiring thought!
And while I feel for the people of Oyand and Orvara and so on, 'well these people did commit mass murder and don’t think they did anything wrong, but it’s in the past now!’ is also not a trust-inspiring position!
'We do not commit mass murder, period, and anyone who committed mass murder has been sanctioned and not permitted to be present’ is the position that can inspire trust. It’s the position we need to be able to go in with.
Whatever your opinion of cleaning, it is a small price to pay for a greater chance of peace in the universe.