Well Allard does not see nationality and ethnicity how you believe it. One line further in wikipedia: "In a podcast segment about immigration and deportations Allard stated his opinion and said that "They will also be forced to leave, even if they are born in Sweden, because they have no natural connection to Sweden. They are not Swedish.""
Also Swedes are an ethnicity: https://en.wikipedia.org/wiki/Swedes
Thanks for providing further context: as I mentioned, I was going off of the available quotes.
Given the party's other points', I'd still say he's not talking about Swedes as an ethnicity but as a nationality, similar to how other non-far-right, conservative parties express their beliefs. I checked the page, and that quote is provided without the context, and since Sweden does not have birthright citizenship, I don't know if he's talking about non-naturalised kids or naturalised people.
Further complications come from the fact that stripping "bad" immigrants of nationality is now an acceptable talking point for liberal parties the world over, and that position is very popular with people of all origins, not just the ethnic Europeans. I'd even argue it's less popular among ethnic Europeans than those of other ethbic backgrounds.
But I'll acknowledge that defending that party's position requires giving tons of benefit of the doubt...