Mr Halligan has described the next US president as a head banger, hardly the words of a responsible adult.
Nevertheless, as the citizen of a free country, he is entitled to hold those views. He is entitled to express those views. But he is not entitled, because of those views, to refuse to do the job that his fellow citizens are paying him to do.
Along with calling the president-elect a brute and misogynist, Mr Halligan says that, in the event of a presidential visit to Ireland, he will have “feck all to do with him”.
That is likely to create problems down the road because a visit by Mr Trump as US president in the near future is quite likely. He has been to Ireland already and owns a golf course in Doonbeg, Co Clare. Indeed, he and his family were given a red carpet welcome, complete with traditional singers and a tarmac greeting from Finance Minister Michael Noonan when he arrived in Shannon two years ago.
However, Mr Halligan intends to protest if the incoming US president pays a visit. Speaking to the Irish Examiner, the minister said: “I understand Enda Kenny dealing or meeting with him, but I would refuse to deal with him if he stood in front of me. I would have nothing to do with him.”
In that event, one of two things should happen: Mr Halligan should either resign or the Taoiseach should sack him or, at the very least, move him to a position where an encounter with the Trump administration would be highly unlikely. As it is, his jobs portfolio would be likely to involve meeting American investors, Mr Trump included.
Resigning as junior Jobs Minister would be not only the honourable thing to do, but the sensible thing to do. It would allow him free reign to speak out.
However, a better and more sophisticated approach would be to actually engage with Mr Trump if the occasion arises and try to persuade him to change his most objectionable views. A perfect example of that was when Barack Obama welcomed Mr Trump to the White House and persuaded him to retain the most essential part of his healthcare reforms.
Another example of doing the right thing was when the mayor of Cashel Michael Browne greeted Queen Elizabeth II during her visit to Ireland in 2011. For a lifelong republican and member of Sinn Féin, the Queen represented everything that Mr Browne opposed, yet he shook her hand and said: “Welcome to Cashel, your majesty.” That showed great nobility on his part. (Sadly, Mr Browne died later that year.)
Engaging rather than protesting can have transforming effects. There were protests aplenty when Ronald Reagan visited Ireland in 1984 but he was welcomed here by the Government and, within a year, had been instrumental in persuading the British prime minister, Margaret Thatcher, to sign the Anglo-Irish Agreement.
If Mr Halligan wants to oppose Donald Trump. the best way he can do that is to act like a grown-up and engage with him and his administration.