While many anti-imperialists hoped to find liberty through national independence, others such as Rabindranath Tagore were critical of the idea of a nation, even if they supported independence. These thinkers observed that nationalism, which they believed went hand in hand with the nation, was often used to justify the imperialism they were fighting against. After decolonisation, thinkers who felt political independence had led to little actual change argued that this was because imperialism still persisted in the ways that the new nations acted and organised themselves.
Nationalism means the exultation of one's nation over others. People praise their nation to the skies and ignore its flaws, believing their nation is inherently superior to all others. This justifies aggressive foreign policy which seeks to dominate other nations and groups. As such, nationalism justifies imperialist conquest and domination of other people. Internal diversity within the nation is stamped out as people are pushed, or even forced, to adopt an idealised "national culture" that destroys other types of culture that don't fit the official model in an act of internal colonisation. Post-colonial nations have engaged in aggressive nationalism and promotion of official national culture at the expense of minorities. Imperialism still persists internally despite formal political independence.
Nationalism isn't always synonymous with nations. Writers such as George Orwell have attacked nationalism as aggressive and imperialistic while asserting the benefits of patriotism: love of one's country without wishing it to dominate all others. Others reject the view that nationalism is aggressive. Figures from Giuseppe Garibaldi to Benedict Anderson argue that nationalism is inherently opposed to imperialism as its fundamental principle is self-determination - people choose to be part of the nation. Attributing coercion in post-colonial nations to the legacies of imperialism strips local people of agency. It pretends they aren't responsible for their own actions, making them doomed to stay trapped in the past acting on the ideas of "the West".
[P1] Nations and nationalism fuel imperialism. [P2] Nationalism is used by post-colonial nations to enact imperialist policies on their citizens.
Rejecting the premises
[Rejecting P1] Nationalism isn't synonymous with nations. [Rejecting P1] Nationalism is opposed to imperialism. [Rejecting P2] Not all coercion by post-colonial nations can be simply attributed to the legacies of imperialism.