Frankly the idea that the Irish weren't regarded as white is nonsense blown up by plastic Paddys in the US who want to larp as oppressed. Just because a group weren't liked doesn't mean they weren't considered white. Calling white people non white was just an insult at the time. It was also done in Canada with the French called non white as a way to call them white trash. The same was done in the UK to the working class.