Why do leftists believe in the conspiracy theory that Ireland is a racist country?

There is a recent thread in Irish press which has been directly borrowed from American media and culture wars that Ireland is a country which actively promotes racial discrimination. This is a fantasy, a hoax and a conspiracy theory. However leftists have promoted this lie almost without any pushback from ordinary people.

How did this evidence free conspiracy theory become so popular without any evidence? Is it to get attention from Americans? Is it because of the Green Party and their middle class brand of leftism getting elected into Government?