So, if he thinks ethnonationalism is a bad idea why does he try to debate whether it can be implemented?

The new strategy is to skip past the debate about whether or not race matters and go right to criticizing solutions. Couching conceptual issues with ethnonationalism in practical objections, which is a way of dishonestly skipping the debate they are sure they'd lose. At least David kind of admitted White Genocide, by saying we will lose our ability to make policy democratically, which is why we either push for separation or get policies for ethnocultural continuity in the short term.

For one I would point out an ethnostate just means a state populated by and run in the interest of a group. Does not need to be a monoethnic monolith, as evidenced by Spencer using Israel as an example. So any policy we take to ensure ethnocultural community makes us an ethnostate, we don't have to kick out all non-whites to accomplish that. I know Richard doesnt think that but people clearly think he does.

I would also use the decline of the USSR and the ethnic repatriation which followed. Very safe.

Moreover, it's important to point out they cant defend the Browning of the West or justify any ideas of assimilation they may hold ("we will deal with the criminals and integrate the rest" well, we police blacks more... not assimilated). The most they can say is that it wont be that bad or we will fix it. Even if you want to disregard the idea of interethnic violence, as Tino Sanandaji would say our nations would fall apart if they take on the traits of these newcomers since there is marginal economic assimilation from 1st to 2nd generation but not much beyond that. We can say violence is inevitable because we can see how violent societies like Coptic Egypt, Brazil, South Africa, Zimbabwe, Hostircal examples of new groups moving in (Sabines), and other internecine conflicts. As well as the crime these groups engage in here, if it is bad enough (Cologne, Rotherham, Rioting). These people would accept violence.