I could understand the backlash if all/most of their money was made in Ireland. Then I see the obligation to give whatever the required tax is, just as I would as an American citizen if I had a popular band who made most of our money here in the States. Thing is, U2 is a global business at this point and they make most of their money in countries other than Ireland.
The same is true about Simon Cowell, Elton John, Paul McCartney and Sting, for example, but they pay all their company and personal income taxes in the UK. U2 could do the same, and indeed, U2 were perfectly happy to do exactly that for over two decades when Ireland had generous tax relief on wealthy artists' royalties, until that is the Irish government changed the rules and made wealthy artists liable to pay their fair share of tax like every other company registered in Ireland.
Also, Ireland has already made a lot of money off of the band (not just through taxes, but also through tourism and other things).
How do we know that? They're not the British Royal Family, you know. I know the Clarence Hotel has made money off of the band's name, but then Bono and The Edge own that.
Who's to say U2 is required to support Ireland at this point? Would people be this pissed if the Beatles were still around and did the same thing to England? Doubtful.
It's not about 'supporting' Ireland, but rather paying their fair share of taxes like all the other Irish citizens, most of whom are decidedly more financially hard-pressed than U2. And I am pissed that the Rolling Stones are massive tax avoiders - and have been for forty years - but then, no member of the Stones goes around asking govenments - including the Irish government - to be more generous with taxpayers money on their overseas aid/development budgets.
Also, do we even know that U2 themselves (i.e. Edge, Bono, Larry and Adam) made this decision? Perhaps it was their business partners/manager?
U2 Ltd has five 'voting' directors - the band members and Baron Greenback - who vote on these business decisions.