because they are everywhere, and they don't care :3 And just because they weren't in the roleplay doesn't mean they didn't exist before.

They will find people who never thought to be found, simply because they're just looking at activity reports and saying "Oh there's something there!" and then going over there, finding any planets that have a good gravitational pull, a couple choice gases, and then they terraform it into a lush, hostile, unbreathable-to-all-but-the-terraformers world.

Hitler had a reason for trying to wipe out the Jewish; whether he just didn't like them (emotional reason), he thought them imperfect, a blight on society (Logical reason [to him]), or something else.
These are much worse. They are not killing you off for any other reason that you are living, and you are on planets that they could live on instead of you. And that's enough reason to exterminate you, because you're competing for real estate.