My view is that it is something that only the north and south can decide. For the EU to pick on it as a blunt hammer says a lot about the character of the EU negotiators, that they are prepared to weaponise an issue, that any rational person can see, has the capability of reopening old wounds.
That they are quite happy to run the risk of reawakening sectarian warfare in order to bludgeon a brexit/nexit agreement gives a clear indication of what sort of governance some are more than happy to embrace.
Not for me I am afraid!