You're wrong they're not alone, social media has connected individuals to others. Today, a person is socialized through screen time, from the moment he wakes up to the moment he goes to bed. The most important change is that he receives instant feedback on all his thoughts and behaviors.
Still doesn't prove your point about the ideology being a result of "oversocialization." On the vast majority of the internet, you will not receive positive reinforcement for espousing Dissident Rightist ideas. Even in spaces that are arguably inextricably tied to race realists/white nationalists, such as theapricity or soyjak party, I've seen anti-Nazis.
In your OG post up top, you say Nazis "appropriate all the codes of the group to which they belong." That makes 0 sense, considering that even just being on the periphery of the Dissident Right for an hour will show you how fragmented and ideologically heterogenous they actually are. The main split being, of course, Christians vs. atheists/pagans/Nietzscheans, but even in other matters, like how a white ethnostate should be achieved, there's a pretty big level of disagreement among different communities in the sphere.
Basically, the general opinion online is very much against WNs/Dissident Rightists, and even Dissident Rightists themselves disagree on many things. So I don't think your suggestion that people adopt these beliefs as a result of community reinforcement holds up to reality.
Focusing on class struggle also means, by extension, addressing demographic issues. The fact that we concentrate a population in one place to be mere cogs in the machine inevitably leads to a reduction in population.
A lot of leftists refuse to acknowledge demographics as an issue at all though. Even ones I've encountered who are against SJWism and could be described as more "20th century Marxists" refuse to talk about mass immigration and its dilution of high-trust societies and cultures, because in their eyes that's just the other side of the same identity politics coin SJWism is on.
Now, if you want to talk about ethnic purity, I think that's an extremist vision that's not so far removed from the vision of feminazis who want to exterminate men.
In what sense is it not so far removed from that?
Feminists want to exterminate men due to social consensus on their fake "oppression" making them resent men for not bending over backwards for them harder than we already do. Ethnonationalists want ethnostates because they see the evidence for multiculturalism and multiracialism being detrimental to their own QoL as natives, as well as undermining their historical cultures and identities. It's really not the same thing, especially when the social consensus is pro-feminism and anti-ethnonationalism