Progressives keep calling for a coalition to defeat Stephen Harper. That's not going to happen—certainly not before the election. In the meantime, however, the NDP, Liberals and Greens could unite behind a plan to oppose the use of terrorism as a wedge issue to divide Canadians.True, these three parties have quite different views on the new anti-terrorism bill and the mission in Iraq, but that is not the issue here. They can continue to support or oppose those measures as they see fit, but the wedge issue is different. It calls for collective action.Terrorism is not just a malevolent act, it is also a psychological phenomenon. Like fire, the act needs oxygen to burn. People must be receptive to the terrorists' message of fear. And the terrorists are doing what they can to make ordinary people like us receptive.So far, ISIS has done very well. Its approach is brutally simple but effective: shock countries like Canada so badly that we cry out loud—and then shock us again…and again.The louder and longer we cry out, the better. Our fear and outrage helps guarantee ISIS the airtime, notoriety, resources and fresh recruits it needs to grow.So why is Harper fanning these flames? Take his suggestion that it is “offensive” for a Muslim woman to wear the veil during a citizenship ceremony—right after a Federal Court judge had ruled in favour of the right.Now, a prime minister is certainly free to disagree with a judge, but let's not be fooled. There was no deep philosophical disagreement here. This was about politics, pure and simple.Harper's comment was crudely calculated to push some hot buttons, especially in Quebec, by singling out these Muslims and labeling them as un-Canadian.Similarly, his jihadist-like rhetoric about the terrorists having declared war on us, hating our way of life or wanting to kill us has no deeper point than to create a climate of fear and mistrust among Canadians, as though we had suddenly been transported back into the Middle Ages.This is not only worrying, it is dangerous. Demagoguery and xenophobia play right into the hands of the terrorists. They raise tensions between Canadians, ghettoize Muslims and help radicalize youth.In short, they not only provide the oxygen terrorists need to carry out their business; they begin to extend the terrorists' reach into our own communities.This kind of wedge politics is nothing less than aiding and abetting the terrorists and it has no place in Canadian politics. We should put an end to it, before things get any worse, but how?During World War II spies found they could learn a lot about the positions of allied vessels just by listening to seamen and/or their families talk about the tours of duty. Finally, a major campaign was launched to check the unguarded talk: “Loose lips sink ships,” declared a series of US government posters:The phrase was intended to provoke a sense of civic duty among Americans and help them realize that everyone was responsible for ensuring the safety of the men at sea. People quickly got the message.We need a similar campaign today, one that is designed to cut off the supply of oxygen to the terrorists by helping citizens recognize their role in the fight against terrorism. The leaders of the opposition parties are well positioned to get this started by working as a team to promote and defend two basic principlesFirst, it is wrong to arm the enemy. Every time the prime minister or any other parliamentarian tries to drive a wedge between cultural or other communities within Canada, opposition leaders should be ready with a coordinated response. They should stand shoulder to shoulder and explain to Canadians, calmly and objectively, how this kind of wedge politics plays into the hands of the terrorists and puts Canadian lives and communities at risk.Second, to defeat the terrorists, we must defeat terrorism. Terrorism is more than a savage act. It is also a psychological state that makes people receptive to the terrorists' message. Citizens have a critical role to play in changing this and it begins with a willingness to learn.Opposition leaders should have a coordinated communications strategy and work as a team to encourage public discussion of terrorism that is calm, informed, and focused on a few key questions: Who are the terrorists? What do they want? How are they trying to get to us? What can citizens do to help?Everyone, the leaders should say, has a duty to learn the facts about the terrorists. The less people know about the perpetrators, the more susceptible they are to their tactics.By working together as a team, the opposition leaders would motivate Canadians to inform themselves, exchange views with one another and, ultimately, help them see Harper's demagoguery for what it is.Nor would anything proposed here prevent these leaders from continuing to hold and debate their different views on the anti-terrorism legislation, the Iraq mission, or other related issues. To make the partnership work, the leaders need only accept the two principles and oppose Harper's brand of wedge politics.Both, I believe, are true.Dr. Don Lenihan is Senior Associate, Policy and Engagement, at Canada 2020, Canada's leading, independent progressive think-tank. Don is an internationally recognized expert on democracy and Open Government. His recent projects include chairing an expert group on citizen engagement for the UN and the OECD; and chairing the Ontario Open Government Engagement Team. The views expressed here are those of the columnist alone. Don can be reached at: [email protected] or follow him on Twitter at: @DonLenihan