There is historical animosity that can be roused easily enough, but generally speaking Irish people don't hate English at all. On the contrary most people don't even bat an eyelid if you have an English accent, they're not really viewed as foreigners in the traditional sense. That being said, English hate and "Nationalism" is being coopted as a pillar of identity for the left, to show how much they disparage imperialism and to counter "the far right" actual Nationalists and anti-immigrationists who are becoming more friendly with the Brits.