Underlying liberal denigration of the new nationalism — the tendency of progressives to describe it as nothing but “racism, Islamophobia, and xenophobia” — is the desire to delegitimize any particularistic attachment or form of solidarity, be it national, linguistic, religious, territorial, or ethnic. As I explained shortly after the Brexit vote, cosmopolitan liberals presume that all particularistic forms of solidarity must be superseded by a love of humanity in general, and indeed that these particularistic attachments will be superseded by humanitarianism before long, as part of the inevitable unfolding of human progress.
For such liberals, any outlook that resists or rejects humanitarianism is an atavistic throwback to less morally pristine times, with the present always superior to the past and the imagined even-more-purely humanitarian future always better still.
Concerned about immigrants disregarding the nation’s borders, defying its laws, and changing its ethnic and linguistic character? Racist!