Opposition TDs only get a limited number of opportunities to hold the Government to account, so it's important they use them wisely.
Which of the great issues of the day did Richard Boyd Barrett, People Before Profit TD for Dun Laoghaire, choose to raise then during Dail question time last Tuesday? It was this: "What is the Taoiseach going to do if Donald Trump is elected? If Donald Trump is elected president of the United States, is the Taoiseach going to allow troops under his direction to continue to use Shannon Airport?"
One might humbly suggest that this is not the most pressing issue facing Irish voters at the present time, in South County Dublin or elsewhere.
In fact, it's probably not even in the top 10.
To be fair to the left-wing TD, he wasn't the only one asking hypothetical questions. Fianna Fail leader Micheal Martin was at it too, seeking clarification on what the Irish Government would do to prevent a possible ban on Muslims entering the US, as suggested by Trump during the businessman's campaign to become the Republican Party nominee; and yes, that was a bit silly too, because the prospect of this ever becoming official US policy is as unlikely as that infamous wall along the Mexican border being built to keep out migrants.
But this was simply a passing remark by Deputy Martin in the course of a longer series of questions about US/European trade agreements.
Richard Boyd Barrett went much further, citing Trump's "frightening, dangerous and extremely alarming" views, and his "racist, dangerous and reckless rhetoric", before adding: "Words fail me as to how terrifying they are and what a dangerous person he is."
Clearly words didn't fail him at all. The word "dangerous" certainly didn't. He used it four times in the space of a few minutes, and again on RTE radio where he attacked the Republican nominee as a "dangerous and vile racist" and "warmonger" and promised protests when Trump visits Ireland next month.
Like Micheal Martin, Boyd Barrett did also ask about the controversial Transatlantic Trade and Investment Partnership (TTIP) deal between Washington and the EU, and his supporters would no doubt blame the media for concentrating on what he said about Trump rather than his concern for workers' rights and the threat to Europe's agricultural base. But he pressed the Taoiseach much less hard on that than did the FF leader; and it's evident from the Dail record which subject most rattled the cage of the left-wing deputies.
Enda Kenny waffled on at length about the benefits of TTIP without interruption. The moment he started talking about Trump, the heckling began. He only managed to get out 19 words before the PBP representative interrupted with a comment: "Does the Taoiseach remember rolling out the red carpet for him?"
Soon the Socialist Party's Ruth Coppinger and PBP's Brid Smith were wading in too. "It is not Deputy Smith's question," the Ceann Comhairle twice had to interject.
Of course, none of this should come as any surprise. Boyd Barrett had hit on the one topic that tickles the fancy of every middle-class social justice warrior - the iniquity of the United States "war machine". They're as obsessed with America as Sinn Fein is with the Brits, and even they've toned down the rhetoric these days, having learned that it doesn't travel outside the republican heartland.
The Left doesn't need to bother, because, as Barrett said in the Dail: "Everybody recognises what a dangerous man Donald Trump is."
Well, obviously not everybody, or he wouldn't be running neck-and-neck with Democratic candidate Hillary Clinton in the polls, but certainly everybody who matters in Irish public opinion.
People in this country have always had an innate bias towards democratic presidents, from John Kennedy onwards. If we had a vote, Hillary would be the runaway winner.
It's still worth examining how "dangerous" Donald Trump really is, however. Taking 1993, the year that Mrs Clinton's husband first took office, as a base, what dangerous things has Donald Trump done in the intervening years?
Let's see. He presented The Apprentice. He bought, and later sold, the Miss Universe organisation. He built Trump Tower. He launched Trump Ice bottled water. He bought some golf courses. He was inducted into the World Wrestling Federation Hall of Fame. He appeared on Sex And The City.
In the same period, for her part, Hillary Clinton was fully supportive at her husband's side as he launched bombing raids in Afghanistan, Iraq and Yugoslavia; as a senator, she backed war in Afghanistan and Iraq; as Secretary of State under President Obama, she pushed hard for the so-called "Afghanistan surge" and was a key mover for the failed US intervention in Libya which exacerbated the migrant tragedy in the Mediterranean.
Whether she was right or wrong to take these positions is not the point (Clinton herself later said that her support for the Iraq War was a mistake). The point is that Hillary is, by any reckoning, a hawk when it comes to military action, whereas Trump is a businessman who has never signed a single order for any action that led to bloodshed.
Yet it's he who is called "reckless", "dangerous", "terrifying", frightening", despite also saying the US has "destabilised the Middle East", berating the coalition forces for lying about weapons of mass destruction in Iraq, and using Libya as a warning against further action in Syria.
Many of the remarks he's made about US foreign policy and Nato could have come from People Before Profit.
So who's the real "warmonger" - Trump or Clinton?
The whole argument of the Irish Left is based on a false premise anyway, which is that there is a significantly more palatable alternative to them than President Trump. They never met a resident of the White House that they didn't despise to some extent, and they're hardly going to want Hillary using Shannon to bomb the US's enemies either.
By fixating on Trump as the clear and present danger to world peace, they're merely encouraging Irish opinion to think of Clinton as the peacemaking alternative, especially when she agrees he's dangerous, warning at her first major foreign policy speech last week that "it's not hard to imagine Donald Trump leading us into a war because someone got under his very thin skin". Even if, when you think about it, it kind of is.
This is symptomatic of the rising tide of silliness which has allowed Salon magazine to compare the growing popularity of Trump to that of Hitler in the Weimar Republic, and in Ireland last week led to an artificial row around whether government ministers would or should meet him when he visits Doonbeg in a few weeks.
It's a further reminder that it's now "unsound" words and opinions which provoke the fiercest and most immediate backlash. Given a choice between someone who has done something with which they profoundly disagree, but who makes the right noises, and one who has never actually done much that is blameworthy but who says things that make card-carrying liberals squirm, it's now invariably the one with the loosest tongue who will be cast into the political darkness.
That's not to say Trump would make a better President than Hillary - as PJ O'Rourke recently quipped, she may be wrong about almost everything, but she's "wrong within normal parameters" - but the truth is that this way of speaking about him has actually reinforced Trump's image as an outsider, a maverick, and it may well propel him all the way to the White House.
Having got there, he probably won't be anywhere near as radical or scary as either his supporters or detractors imagine. Not that this inconvenient fact would stop the Left from protesting all the same. It's not Donald Trump that they hate. It's America.
The Taoiseach should have avoided the trap set for him last week. It's always foolish to indulge populists such as Richard Boyd Barrett in their ceaseless quest to turn life into one long student demo.