back when i was an internet arguer a frequent argument was
"Is that genocide?"
a lot of it goes down to completely subjective unknowable things like, whether the perpetrator 1. intentionally wanted to 2. exterminate an entire population (and there what is a 'population' must be be ethnic? what about religious or political populations?
So if the mass slaughter was unintentional, OR if it did not seek to or achieve a complete extermination, then it's not genocide, and so I've heard people say the systematic de-peopling of the America's was not genocide because most of it was through disease and so unintentional, or that the trans Atlantic slave trade which killed both directly certainly over 20 million and by some estimates over 100 million people was not genocide at all, just kind of an externality,
honestly it get's fucking ridiculous and people who do that should never be given any responsibilities because they're nazi jurists in waiting