"bunch of Brits (maybe some Americans thrown in), the same as me, (I have Irish family connections, but I was born and spent the most of my life in Britain) deciding and pontificating on what is best for the Irish"

No, we are pontificating that the people involved should decide for themselves.

Your WW2 question. The fight would go on as long as there was a will fight.
When a majority preferred things to remain as they are, who would have the right to deny them?