MY recollection of Nicola Sturgeon at university is that she was surprisingly poor at debating. Surprisingly, because she was then as politically interested and committed as she has remained and – as she still is – articulate and forceful in advancing her views.

The problem was that her views were always exactly what happened at the time to be official SNP policy, while competitive debating required the speaker to make the case for whatever side of the motion she had been given.

That kind of debating, in the chamber of the GUU or the Oxford Union, is often characterised as play-acting, which is what it was. Even so, it was more useful and instructive as a rehearsal for real life than actual student politics, as conducted by the Students’ Representative Council or the National Union of Students, which was invariably a kind of gestural Corbynism avant la lettre.

That’s because debate – precisely because it is pretence, and not necessarily what you actually believe – requires the participants to think critically about the arguments for both sides of the proposition, and be ready to counter objections. When I’ve said, as I often have, that the First Minister seldom provides any indication of what could be called thinking, I don’t mean that she’s thick, or doesn’t consider her strategic options, but that she doesn’t habitually engage in that kind of critical evaluation.

That, of course, may make her a more effective practical politician. But it gives me pause whenever she says something with which I wholeheartedly agree, as she did the other day. Emerging from Downing Street, where she’d given the Prime Minister a bottle of Misty Isle gin from Skye for Christmas, she expressed the opinion that the Government’s immigration policy was “an act of vandalism on Scotland’s economy and public services”.

Economically, it’s straightforwardly empirical: immigration contributes more to the Scottish (and UK) economy than it costs – much more. And while Ms Sturgeon’s claim that a 50 per cent reduction in EU migrants would send Scotland’s population into decline and that forecasts suggest a reduction of 85 per cent is, like all claims about the future, unverifiable, it seems plausible.

I also entirely agree with her opinion that most immigrants enrich society in ways that may be less obviously measurable in economic terms but may be, for all that, more important. I’m thinking mainly of food and music, but you can draw up your own set of cultural priorities.

Yet, rather than congratulate myself and Ms Sturgeon on our enlightened opinion, which is clearly the right one, anyone seeking to make that case should ask: what are the objections to this view? And if they don’t seem obvious, why on earth doesn’t everyone agree with me?

Willingness or ability to do that – notably on the issues of independence and Brexit – seems to be in short supply. But plenty of reasons could be advanced to counter the First Minister’s pronouncements on immigration, however much I may agree with them.

The first, and cheapest, is that the proposals drawn up by the Westminster Government are, in general, almost exactly the same as those given in Scotland’s Future, the independence White Paper published in 2014. It too advocated parliamentary control of immigration, robust border controls, a points-based system, assessment of skills, the repatriation of failed asylum seekers, and all the rest of it. It even proposed to dictate which area of the country people could settle in. But to point this out is merely to attack Ms Sturgeon for inconsistency with the stated policies of the party she leads.

A politician (sensibly) making all the hay she can out of Brexit, when every point she raises – from the legitimacy of a referendum to the difficulty of disentangling laws, or the case for customs unions to unrealistic claims about future prosperity – could as easily be applied to independence, is not going to be held back by a little thing like that. In any case, I suppose the SNP could revise its policies in line with what the First Minister says.

What’s trickier is persuading those who don’t share the liberal view of the benefits of immigration. The First Minister doesn’t subscribe to the economic justification I would advance, which is that – as with most things – the market is a better regulator of immigration than government and that any fixed targets are counter-productive.

Opponents of immigration can be defeated on most economic arguments, because they’re demonstrably wrong. Immigrants aren’t a cost to the welfare system, and there are sectors of the economy, including agriculture, catering and the NHS, to which they are crucial. Even the claim that immigration holds down the wages of the poorest is an argument for it as a boon to the economy in general, though not one that anyone left of centre cares to advance.

Much of the hostility to immigration, however, has more nebulous causes. Some of it, alas, is simply racism or prejudice, which should always be challenged. But the historical reluctance of politicians to address the subject, assuming that it is always nothing but bigotry (you will remember Gordon Brown’s awkward moment on this issue) is in large part what has inflamed public opinion.

Cultural concerns can be real without being racist. Schools where many children speak English as a second language face challenges and costs which, with adults whose grasp of English is poor, also affect the courts and social services. Radical Islamists are a tiny subset of British Muslims, but the danger they present is alarming. The treatment of women by some immigrant communities is at odds with British values, and sometimes laws. The same can be true of drinking habits, or “street” culture.

The natural tendency of people to settle in areas where others from their country of origin already live can lead to a place’s character changing markedly (think of UK residents on the Costa del Sol). The refusal of the authorities to take complaints about that seriously can lead to social breakdown. The First Minister need look no further than Govanhill, in her own constituency.

I, and I assume Ms Sturgeon, believe that the benefits of immigration, cultural and economic, outweigh these objections. But they deserve more than a glib soundbite and a few tweets. It’s futile to pretend that they are not there, or that they will go away without doing some hard thinking and having a genuine debate.