"The Irish were slaves," is an argument made by right-wing Americans and has little to nothing to do with this discussion.

That is an argument used to belittle the experience of African-American's with slavery in the US.

It is quite a different thing for Irish to talk abot the discrimination they faced in Europe at the hands of the English. That is not even a topic among conservative Americans because it does not concern Americans in their domestic oppression olympics.

The point is that Europeans have to be allowed to talk about the fact that discrimination and racism has a different history in Europe from America, and you cannot apply American perceptions and concepts about racism to Europe.