tbf, and it's often the same in Wales, there is a lot of resentment of the English. I never knew there were so many Slovenia fans in Wales...
However, a lot of that is similar to here, really. I've got used to saying in both Scotland and Wales that I hate London, too. The deprived areas see their politics ignored, a lack of investment, and they see stories centred around London, with not even as much of a lack of understanding of their issues, but a lack of care - the establishment just isn't bothered what they think.
So they equate that with Englishness.
The best way to change that, is to start noticing them. For that matter, not dismissing the SNP as an irrelevant joke, too, but including them in decision making. The best way to reduce nationalist influence is to being them into the fold.