against the "legitimate right of a people to self-determination"

I had a twitter exchange with a man who accused me of being an anti-semitic shithead because I did not recognize the legitimacy of the Jews right to self-determination.  I called him a general shithead and accused him of being the anti-semite. Things went from there, in the usual twitter way.
However, if I had not felt like insults were in order, I might have surprised him by saying that I am opposed to the principle of self-determination period. I think that every nation state that grounds its legitimacy in ethnic identity is on the road to fascism. Sooner of later such a state will either have to re-constitute its legitimacy or become a racist state, and as such, begin suppressing criticism and begin the process of institutionalizing second class citizenship.
The principle of the nation state was, up until the 1840s, I’d say, almost never identified with some ethnic group, rather than with a royal family, or a religion. The Atlantic revolutions identified something different, what Rousseau called the popular will. But that will was not identical to being, say, White male and protestant – even though the U.S. was, of course, founded by White Males who were predominantly protestant and often slave owners.
The romantic state, as I’d call it, changed this formula by up-fronting ethnic identity. Germans for Germany, Italians for Italy, etc. Yet this formula was by no means unproblematic. First, there were definitely Germans outside of Germany – the state Bismark made – and there were definitely Germans who weren’t ethnically German inside of Germany. Secondly, the same wave that resulted in the founding of these states resulted in some quasi-democratic form of governance – a Reichstag or Parliament – which gave non-ethnics certain rights to political expression and pathways to governance.

We know how the story went in Europe.

In the U.S., the person who did the most to amplify and internationalize the “self-determination” talk was Woodrow Wilson. Indeed, Wilsonian language is still used when the claim is that Jews – or Palestinians, or Hutus, or Japanese, etc. – have a “right” to self-determination. Although the fact that Wilson was a racist president, which was repressed by the old, liberal mainstream view of American history is now out in the open, we don’t see how that racism permeated his internatlonal outlook. But the man who thought Birth of a Nation was a historically accurate film was the same man who thought ethnicities had special rights. Through the Wilsonian lens, the founding of the U.S. was especially a matter of White Christians. The Pat Buchanan/Trump view of American history is a direct descendent of the Wilsonian ideology.
The romantic nation-state seems to follow an inexhorable logic, in which the very liberatory culture that accompanied the founding of the state is sooner or later alienated from the power establishment that runs the state. That power establishment, in turn, begins to attack that liberatory culture as anti-German, or anti-Italian, or anti-American – or anti-Jewish, or anti-Palestinian. Not to get all Hegelian here, but the history of the last two centuries does seem to show that there is a logic here, or at least, that the structuration leads to similar results.
This all seems obvious to me. But maybe it isn’t obvious to everybody. I don’t know.