Anarchists are not nationalists, in fact we are completely against nationalism. We don't worry about where your granny was born, whether you can speak Irish or if you drink a green milkshake in McDonalds on St Patrick's Day. But this doesn't mean we can ignore nations. Irish history bears a lot of witness to this. The Kurds, Native Americans, Chechins, and many more have suffered also - and to an amazingly barbaric degree.
National oppression is wrong.
It divides working class people, causes terrible suffering and strengthens the hand of the ruling class. Our opposition to this makes us anti-imperialists. Today, in most parts of the world, nationalist movements no longer fight for victory over their enemies. They seek compromise. The last few IRA bombs have not been aimed at getting the British state out of Ireland, they have been attempts to force the British to talk to Gerry Adams and Martin McGuinness.