Crimes against humanity/war crimes are on different scale.

You're getting way too cerebral for this thread. The people who say "they're all equally guilty" don't care about such considerations. They're just trying to make a blanket moral relativism argument.

Which basically goes: "They're all bad to some degree, therefore they're all equally bad, or at least we can stop focusing on the one that's obviously much worse than the others."

It's not an argument at all really, but more like an emotional appeal.

Makes sense. Such views seemed always so reductionist to me that they are basically nonsensical and arrogant. You are correct.