Nicholson referred to the "rhetoric" of the Islamic State in Iraq and Syria, also known as ISIS or ISIL, in his speech in the House of Commons.
"ISIL has declared war on Canada," Nicholson said. "By name, it seeks to wage its jihad against our people. No matter how these facts are communicated, Canadians know that the leaders of the opposition parties will dismiss that and with that, they [are] dismissing Canadian values."
He added: "These threats cannot be wished away by pious rhetoric. We cannot speak of supporting the mission and our soldiers in one breath … while voting against them in the next."
The New Democrats proposed amending the motion before the House that calls for support for the combat mission.
The prime minister doesn't require the support of the House to authorize a combat mission but Stephen Harper has made it a practice to put a motion before MPs when he deploys the Canadian Armed Forces into combat.
The NDP motion calls for the government to end the combat and training missions in Iraq and Syria as soon as possible, but continue to contribute through military support for transporting weapons.
Humanitarian aid debated
The motion also includes calls for the government to:- Boost humanitarian aid.
- Work with Canadian allies in the region to stabilize neighbouring countries and strengthen political institutions.
- Increase funding for refugee resettlement.
- Work to prevent the flow of foreign fighters, finances, and resources to ISIS.
- "Continue to offer its resolute and wholehearted support to the brave men and women of the Canadian Forces who stand on guard for all of us."
Green Party Leader Elizabeth May acknowledged Canada is one of the largest donors to humanitarian aid for Iraq and Syria, but noted it's a drop in the bucket when faced with four million refugees.
She questioned what it was about ISIS that makes the government want to send in troops when Canada didn't respond with its military during the four-year war against the Syrian regime led by Bashar al-Assad.
"The reality is we have ignored the crisis in Syria, and now we are interested in protecting people from ISIS. Who is going to protect them from Bashar al-Assad?"
New Democrat foreign affairs critic Paul Dewar also pointed to the ongoing conflict in Syria and the risk of new conflicts arising without proper humanitarian aid and development.
The Canadian government had said early in the Syrian civil war that it wouldn't interfere because there was no clear successor to Assad.
Dewar quoted University of Waterloo professor Bessma Momani.
"'If you don't provide sustainable institutions that can fill that vacuum, it will just be another acronym that will fill that space,'" Dewar told MPs.
"I couldn't agree with her more. That's where Canada's expertise and Canada's potential lie. We can save lives, we can build peace, to help the people in Iraq."