Why is that hopefully? Their beliefs have not an ounce of jewishness in them.
I honestly believe that there is nothing implicit in the definition of white nationalism that is anti-Jewish (seeking to work against or harm Judaism or the Jewish people). I agree that being a white nationalist would be necessarily unjewish (going against the teachings of Judaism) but not necessarily anti-Jewish. Same with eating non-Kosher foods. The majority of WNs today are anti-Jewish, and that is a shame.
There is absolutely nothing Jewish about supporting WN agenda.
This I would disagree with. I think it would be entirely possible to support a white nationalist agenda
for gentiles and to still be Jewish in the same way that it would be entirely possible to support an agenda for gentiles to celebrate U.S. Independence Day. For a Jew to actually be a WN or to celebrate U.S. Independence Day would be bad because it would be unjewish.
That's like hoping Jews and (lehavdil) nazis can be friends one day.
Well, not quite because Nazism was a socialist and totalitarian ideology. Socialism and totalitarianism are evil. But Nationalism is not necessarily evil. It can be good.