but mostly because they think it's part of the UK anyway
This has become apparent. And nothing is more likely to get Irish people's backs up than this attitude.
The EU is very popular here in Ireland. Membership has done positive things for the country. Approval ratings are high (80/90 per cent). Bright young graduates go off to the EU and build careers there. We have representation in key roles. The EU is an important mechanism through which the Irish have established themselves as a modern, independent country
Ties with the UK on the other hand are linked to a negative past where Ireland got fucked over by colonial big boys. No one has any interest in a return to that.
The Irish were very, very happy with the status quo and brexit is a total PITA for us, especially as we've just come out of recession.
The idea that Ireland would 'choose' the UK over the EU is plain ridiculous.
The ROI and nationalists in the north are very invested in avoiding a hard border, because of what it would mean for trade, but also because it allows nationalists to feel and identify as Irish if they like, under the terms of the GFA.
For what it's worth, I'm not sure the ROI give too much of a fuck about NI nationalist sentiments, but they desperately want to avoid a return to violence and any disruption to trade.
The DUP want some kind of magical reality where they get to brexit, retain exactly the same relationship with the rest of the UK, yet somehow avoid any disruption to the farming trade which is their bread and butter. They give no fucks about the GFA and never have.
Of all the clowns out there who want to have their cake, eat their cake and will tantrum if they don't get their way, they are the worst.