You say that because you have no problems with nationalism, as long as it's done by the people you like of course - so much for a stateless, classless society.

Edit: My accusatory tone in the last sentence was kind of pointless. Choosing to support nationalisms around the world because of x and y reason do not mean that you support nationalism in itself, be it from we have to work with what we have/"critical support" angles or genuine approval of nationalism.

Proletarians tending towards nationalism feel like they have a reason for it - be it because they think the world outside the borders is a threat, be it from capitalist competition hurting the local bourgeois, immigrants scary or being targeted for daring to even consider reformist politics. I see it as a bit of a pointless endeavour for communists in the west - to critical support this, critical support that. However, material aid is a different thing - libs' NGOs spread around their ideology and supporters' economic interests to all corners of the world from material aid (or promises thereof) to avalanches of propaganda. A communist organization donating to proletarian organizations in need of it (like say medical aid to Cuba) or a union blocking weapons shipment to warzones does work to build a movement, no matter how weak we are atm, without needing to compromise on one's principles or going "it's good when they do it".