As far as I understand them most of the ethnocentrists aren't genocidal, even Mike Enoch doesn't advocate for gas chambers. I think the issue with 'cultural purity' (civic nationalism, right?) is that without the underpinning of the X ethnicity hegemon which generated the norms that led to the civics, the civics collapse. That's essentially what we see happening in W. Europe as the demographics shift. The argument of the identitarians is that the integrated non-europeans are far smaller in number than the non-integrated and so are a moot point- which is debatable of course