The debate over what to do about the asylum seekers crossing our southern border — revived this week after the Quebec government worried aloud about its ability to deal with a possible surge of arrivals this summer — is serious, tawdry and dangerous.

On Wednesday, for instance, Conservatives celebrated when Prime Minister Justin Trudeau acknowledged in the Commons that crossing the border between official points of entry could be called "illegal."

(The government typically refers to "irregular" border crossings. The Conservatives insist on calling them "illegal.")

NDP MP Jenny Kwan later stood on a point of order to argue that, according to a strict reading of the Immigration and Refugee Protection Act, the people crossing the border at places like Roxham Road in Quebec aren't committing a crime.

Conservative MP Michelle Rempel accused the NDP of quibbling over "semantics," but the adjective "illegal" is obviously meaningful to the Official Opposition. And when applied to human beings with families and children who might have excellent reasons for fleeing their home country, "illegal" is at least a fraught term.

Playing politics

The Conservatives, who describe the ongoing border crossings as a "crisis," would like the government to table a plan for resolving the situation. They went as far as tabling a motion in the House this week calling on the Liberals to do so.

But — in the classic style of opposition motions — the request for a plan was buried in text that would have had the government acknowledge its "failure to address the crisis" and "admit the Prime Minister's irresponsibility of tweeting #WelcometoCanada to those seeking to enter Canada through illegal means."

Immigration Minister Ahmed Hussen says the government has dispatched senior officials to work with the American diplomatic mission in Nigeria after Canada sees a growing number of Nigerian asylum seekers using American travel visas on their journey to this country. 11:05

And so Liberal MPs declined to support the motion in a vote on Tuesday, and so Conservative MP Ted Falk stood in the House on Wednesday and lamented the prime minister's refusal "to even commit to a plan."

The Conservatives also charge that the irregular arrivals are "queue jumpers," a description the government rejects.

The Liberals argue the Conservative and NDP proposals — respectively, to declare the entire border to be an official port of entry, or to unilaterally suspend Canada's border agreement with the United States — are both irredeemably flawed. And the situation is certainly complicated, legally and practically.

But writing down and publishing a detailed plan could still be useful.

In the meantime, each side is warning the other about where all this might be headed.

'The flames of fear and division'

"I recommend that my colleague choose his words carefully, because false information and incendiary rhetoric only fan the flames of fear and division," Transport Minister Marc Garneau said Tuesday, scolding Conservative MP Pierre Paul-Hus.

"I'm worried that the dialogue in Canada is going to switch from 'how we do immigration' to 'if we do immigration,' " Rempel told CBC radio's As It Happens that same day.

On Wednesday, Trudeau said it was "completely irresponsible of the Conservatives to arouse fears and concerns about our immigration system and refugees."

But Rempel contends that it's the Liberals who could be inciting division.

"As someone who supports compassionate, planned, orderly migration, and sees it as a key to sustaining the Canadian economy over time when done properly, legally, and safely, I worry that by abdicating the responsibility to do this, it is actually the Liberal Party that is creating divisiveness in the country," she told the House this week.

More than 6,000 people have crossed the Quebec border seeking asylum so far in 2018 and officials expect the surge to continue with the onset of warmer weather 7:34

Trudeau's tweet and Trump's edicts

Canada takes pride these days in not being the sort of place where such divisiveness dominates. But you don't need to look far here to see how large-scale, unplanned immigration can trigger something ugly and destructive.

In the United States, migration has helped to inspire a nativist litany of grievances that is warping American politics. In Europe, it has helped to birth a new era of nationalism. All sides should be aware of the forces at play here.

However much the prime minister's tweet on January 28, 2017 acted as a beacon to those seeking refuge, policy decisions in the United States are no doubt giving people good reasons to flee.

But that American approach isn't likely to change soon. On Thursday, the Trump administration announced that 9,000 Nepalese immigrants will have to leave by June 2019. And even if Trudeau had never hashtagged a message of welcome to the world, the federal government would still bear the responsibility for managing the border.

Liberals can point to the emissaries they have dispatched to dissuade would-be travellers, but such efforts will be discounted if the rate of crossings doesn't decline. The Trudeau government can point to the funding and resources it has committed to dealing with the new arrivals, but ultimately the Trudeau Liberals may find they have little room now to quibble with the premier of Quebec, or to suggest that it's the province that should be doing more to accommodate asylum seekers.

If social services in Quebec are noticeably stretched, if immigration procedures bog down, if community tensions rise, Ottawa will be blamed.

Of course, all of this — the number of people crossing the border, the processing and integration of those people while they're here, the language being used to talk about them — are ripe for political exploitation.

Responsible critics have a duty to avoid overstating the danger here. Responsible governments have a responsibility to limit the grounds for concern.