I disagree with some points of the article, most notably this one:
The left fears nationalism in general
The left do not fear nationalism. In fact, they actively support and promote nationalism, especially in the case of Arab nationalism and nationalism in south-American countries.
Nationalism is not the same as patriotism. Patriotism is love for one's country, regardless of nationality (ethnicity) of the people who are part of it. Nationalism is love for one's nation, regardless of the country they live in.
There are nationalists in the US. White and black supremacists, anybody who thinks of "whites" as a people or who considers "blacks" a distinct people. And while supporters of white nationalism can be found on the (traditional) right, supporters of black nationalism are very vocal on the left. Current leading Republicans have no support among either of the two groups.
But most American "nationalism" is really patriotism. What Americans are proud of has no race. And skin colour does not make or undo the American. Patriots are found on the right.
It is PATRIOTISM, love for one's country with no attention paid to skin colour, that the left fear. The left abhore equality (because it takes away the problem they want to solve). That's why they support policies that require classifications of people according to race (NOT culture, race). How many policies do Republicans currently promote that require statistics on how many Americans are white, black, or something else? How many policies do Democrats currently promote that require such statistics?
The left has been fine with nationalism for a long time.
Where do you find more supporters of the state of Israel, where Jews, Druze, and Bedouins live and fight together against the common enemy?
And where do you find more supporters of the PLO, an Arab nationalist group who want (and they openly say so) an Arab-only "Palestine"?
(Incidentally, "Palestinian" propaganda brochures always show "Palestine" with pictures of white and black children playing together. In reality Israel has black and white citizens, whereas the PLO territories are un-mixed. Israel's blacks are Jews from Ethiopia and New York. Palestian Arabs are white only.)
Where do you find more supporters of an Iraq governed by both Kurds and Arabs?
And where do you find more supporters of an Iraq governed by Arab nationalists?
I think it is obvious that the left do not "fear nationalism". In fact they love it.