Why do many leftists view Nationalism as incompatible when at times it has been essential in unifying the people?

Why do many leftists view Nationalism as incompatible when at times it has been essential in unifying the people?

Wew

Gosh I wonder why

Quite the contrary, the overwhelming majority of the left sees nationalism as compatible with post-capitalism, as resting on their buffoonish idea that there can ever be such a thing as state division under an economic system that doesn't mandate it to function.

For what purpose? The conclusion of the USSR was that it was merely the "eastern" bourgeois counter-weight to the "western" original bourgeois enclave. It merely supported other nations under the condition that they be such left-nationalists and acted with their economic support against the blue bourgeoisie, together with their red bourgeoisie. Even the anarchists, whom essentially has as much blood on your hands as the Stalinists do with all the young women and men whose bodies were decomposed in the mountains of Spain as martyrs were ultimately the victims of their attempts to "do" their idea of socialism through the confines of a bordered stronghold (which, needless to mention, resembled a state in virtually every sense of the term including their own).

The only successful revolution to bring us towards post-capitalism will be the one that formally abandons the idea that they can baby the masses with their comfy nation states into accepting a world without one (communism). They will bring us quicker to an ultra-globalized neoliberalism than they will bring us to communism with their "solidarity among muh anti-imperialist, sovereign """"socialist"""" states).

1. Because nationalism is always tacitly exclusionary or racist (even when it's in the narrowest, legalistic sense – not being allowed to do things and go places because you have the wrong paperwork), and if it isn't it can barely be called 'political' nationalism; it's just a stupid fetish. Even if it 'unites a people', it doesn't unite 'the' people as something oppressed by nations and borders.
2. (Which is sort of the same point as the last one) Modern nations only came about with the advent of the capitalist era and only exist in the orbit of capital, as something that meets the market's requirement for organised territorial legal entities and centralised bureaucratic apparatuses.
3. French Republican nationalism (at least in its revolutionary periods) is an interesting example. There's always been a kind of contradictory 'French universalism', which asserts a transnational, even anti-national 'natural' law behind national particularisms. So the Communards could write about the 'great people that storms Bastilles and destroys thrones' at the same time as saying they were 'fighting for the freedom of the world'.

terrific historical materialism there

...

Nationalism can unify everyone within a nation-state, but can also unify everyone outside your state against you.
Part of the reason the Red Scare/Cold War was so bad was that socialism was forever tied to a nation-state and thus construed as a national enemy of all capitalist states. It's a great way to sabotage an ideological cause when you can freak everyone out with fear of a foreign state.

It spread democracy all across europe. I'd say the imperialism was fucking worth it if you compare it to the horrific regimes that ruled before.

It didn't spread democracy, it spread some co-opted version of liberalism. Often by appointing autocrats sympathetic to liberalism.

Nationalism is cancer, it only promotes autistic conflict between worthless morons who take their nationality as their self esteem.

It makes also delusional people who say they prefer their countrymen over some other country's men when taht clearly is false because not everyone is the same fucking person.

But the right wing never really realized that, their lack of control over life has forced them to create a defense mechanism where they generalize about entire groups of people in a way to tell themselves and feel in control