Senate of Canada Sen. David Tkachuk was invited to address a crowd of protesters on Parliament Hill on Feb. 19, 2019.

OTTAWA — A Conservative senator is facing criticism after he encouraged a crowd of protesters to "roll over every Liberal left in the country." Saskatchewan Sen. David Tkachuk made the comment while addressing a few hundred "United We Roll" protesters on Parliament Hill Tuesday. The senator said he was invited to speak by the Greater Ottawa Truckers Association, a municipal lobby group.

Pro or anti #pipeline no one should ever encourage a crowd to run over their political opponents. Senator David Tkachuk did just this today at the #UnitedWeRoll rally. Shameful behavior @SenateCA#CDNpolipic.twitter.com/S5C0aaga5c — Patrick McCurdy (@pmmcc) February 19, 2019

"I know you've rolled all the way here, and I'm going to ask you one more thing: I want you to roll over every Liberal left in the country," Tkachuk told convoy-supporting protesters. Cheers erupted from the crowd. "Because when they're gone. These bills are gone," he said, referring to Liberal government legislation proposing an oil tanker ban in northern British Columbia and another to rehaul the pipeline review process. Tkachuk said he felt obliged to greet the attendees, many of whom travelled from his home province to voice their frustrations about a variety of federal policies from energy development to immigration. "People aren't driving all the way across the country to have lunch with their neighbours," Tkachuk told HuffPost Canada on Wednesday. "They're driving across the country because they're worried about losing their home and educating their children. And that's why they came here." The "United We Roll" convoy started in Red Deer, Alta. last Thursday and arrived in Ottawa Tuesday for two days of demonstrations. The theme centred on a pro-pipeline message, but speakers and signs hanging from trucks touched on criticisms of the United Nations' global compact for migration and Canada's refugee policy. Protesters also voiced their concerns about the carbon tax and its potential impact on the livelihoods of truckers.

Zi-Ann Lum/HuffPost Canada Many signs were displayed as part of the "United We Roll" convoy rally on Parliament Hill in Ottawa on Feb. 20, 2019.

A sign is affixed onto a truck at the "United We Roll" convoy.

Zi-Ann Lum/HuffPost Canada

Zi-Ann Lum/HuffPost Canada

Zi-Ann Lum/HuffPost Canada

Adrian Wyld/Canadian Press A protester wears a "Make Canada Great Again," hat as a convoy of angry Albertans and other westerners rolled up to Parliament Hill in Ottawa on Feb.19, 2019 to protest federal energy and environmental policies.

Conservative Leader Andrew Scheer and People's Party of Canada Leader Maxime Bernier both delivered speeches and posed for pictures with rally attendees. Cullen is more bothered by the presence of two federal leaders than he is by Tkachuk's comment. Scheer and Benier stood before the crowd "with the authority of a national party," he said.

As a representative of a federal riding with a resource-based economy, Cullen said he understands the frustration some western Canadians feel about the slow pace of major projects approvals. But, he suggested, Scheer and Bernier had made costly and short-sighted calculations when they lent their support to the rally. "It did damage to those people who do want to see more natural resource development," the NDP MP said, calling the yellow-vest movement a "very xenophobic crowd" to roll with. Conservative MP Pierre Poilievre also addressed the protesters. "It was a pipeline rally," Poilievre said, sidestepping a question about the involvement of the yellow-vested protesters. He was there, he said, "because I support pipelines." But that explanation doesn't wash with Cullen. "You'd have to be deaf, dumb and blind to not realize it was more than just about pipelines," he said. Watch: Protesters explain what they're frustrated about