Irish was the main language spoken in Ireland up through the late 1800s, and likely would be today but for the troubled history of the island (aka British rule). Irish has nothing in common with English. Comparing that to the relatively similar Ukrainian and Russian languages is silly.
Ukrainian is a distinct language from Russian. French, Italian and Spanish are all similar to each other. Does that give one of these nations the right to force its rule on the others? Try telling the Ukrainians that they are Russians.