The ideologues of the Swedish upper-class in Finland were producing all kinds of propaganda about how the Finnish people needed to be pruned of its antisocial elements. The murder of Red women, who were the demography of prisoners that suffered the most, was justified with the need to prevent them from giving birth to new criminals.
And if not all militant workers were killed, it was mainly because the workers of Germany overthrow the Kaiser, making the generals of White Finland suddenly recognizing the possibility of retribution. Until that, they were planning a parliamentarian monarchy with very restricted voting rights, while the tens of thousands of prsioners remained in the camps dying by disease and starvation.
But I agree, maybe genocide is a harsh word, but then precedent of Srebnica says otherwise. And there was a ethnic element, while the White Finns, including old tsarist collaborators like Mannerheim, were suddenly fervent Finnish nationalists (after having, as late as the previous summer voted against the Power Act and siding with the Russian intervention to stop independence) the fact is that their leadership and a lot of the rank and file (ostrobothnians, primarily) were in fact Swedes, and that probable a main reason for the brutality unleashed on the rebellious Finns.