Further, yes Ireland can set their own tax rate, however either has to be fairly applied across the board ie every company gets taxed at the same rate. A figure quoted today said Apple were paying £50 tax for every £1,000,000 profit. This is considerably lower than other companies in Ireland were being taxed at. This is the root of the problem here, not that Ireland has low taxes.

I'm taking it from the tact of "it's ethical for two groups to arrive at whatever deal they'd like, as long as no individual is being deprived of his/her rights."

In other words, it doesn't have to be applied across the board to every company at the same rate. If it were, it's unlikely that Apple would have chosen this arrangement with Ireland.

You might argue that the people of Ireland are somehow being hurt by this lower rate of taxation, but the money would have gone to the GOVERNMENT of Ireland, and probably not benefitted the people much at all, except some nominal amount to placate their desires and win popular appeal.

I'm super fringe when it comes to taxes and ethics, though, so... no need to agree with me.

Except Ireland joined the EU and with the agreed to the fair and equitable taxation policies. Simply said the agreement is to tax all businesses alike within your borders. The idea is to promote free trade by preventing state aid. So for example the Irish government cannot give a construction company(A) special tax rate that would be lower than that of another construction company(B) as this would give (A) an economic advantage allowing them to submit lower bids for work than (B). So to ensure a level playing field for all you must treat companies equitably, so corporation tax is a flat rate on profits for the small corner shop to the large multinational.

The money would go to the Irish Government, which isn't some African corruption ridden state, so it would have gone on improving things in Ireland.

For example it costs approx €1bn a year to maintain their water supply. As an austerity measure they have had to recently introduce specific water rates rather than cover it from general taxation. This tax bill (if paid at the time it was properly incurred) could have prevented the need for that for a decade or more, and at a time when there was an economic crisis it would have meant consumers having more money available. Instead it can now only be used by the Irish government to pay off their deficit, which is a long term benefit to the Irish people.

Except the payment would be made by Apple to Ireland and not to the EU. And specifically Ireland can only use it to pay down their deficit. So they are kind of doing Ireland a favour here, Ireland get to claim the tax from Apple but by contesting the original ruling they can try to curry some favour with Apple to prevent them moving their business entirely from Ireland.