Ireland remained a dominion of the UK until 1948. But whereas in WW1, where the dominions entered the war with Britain because an act of agression on one was considered an act against all, this was not the case in WW2.
De Valera was a pragmatist who had a difficult job leading the independant, but still very fractionised Ireland. He had tried to reign in the people in his governemnt who had wanted to side with the enemies of the British realising that Ireland's independance would be in jeopardy if the UK was invaded. In fact, it was quite apparent that Germany had no intentions of respecting Ireland's neutrality had the planned invasion of Britain been successful. Some of his actions such as signing Hitler's condolence book should be seen in the light of diplomatic relations.
In fact, despite relations with Nazi Germany, the Irish were more helpful to Britain than their neutrality would have normally demanded. The return of Allied airmen and seamen where Axis personnel were interned, the allowed use of Irish airspace and the positioning of Allied radars on Irish soil all demonstrate this.
Which makes the handling of the Irish Governemnt to these soldiers inexcusable. An apology should be given.