I don’t think the duration of a State’s history is a determinant of the fidelity its citizens owe to it.
That may be what you think, but thousands of loyal Irishmen disagreed with you.
2) The BBC News article repeatedly referred to "the Republic of Ireland". No such country exists, nor has ever existed.
In the UK the Ireland Act 1949 provided that "Republic of Ireland" is the official name of the state under UK law. So there.