In this context "English nationalism" means being in favour of an end to the Union with Scotland (and Wales, if that's what the Welsh want).

Nothing in the least racist about that - after all that's what Scots in favour of independence want, and they can come in all colours and from all kinds of ancestral homelands. I understand you don't have to wear a kilt and have a Caledonian pedigree stretching back yonks to support the SNP.