Last weekend’s rally in Washington, D.C. is being called the largest climate change rally in history. At least 35,000-40,000 people from all over North America came out on what was an unseasonably cold and windy winter day to demand that U.S. President Barack Obama deny approval of the Keystone XL pipeline and make good on his stated intentions to take serious action to address the climate crisis.

The rally included speeches by Bill McKibben of 350.org, who told the assembled crowd, “For 25 years our government has basically ignored the climate crisis: now people in large numbers are finally demanding they get to work…We shouldn’t have to be here – science should have decided our course long ago. But it takes a movement to stand up to all that money.”

Sierra Club Executive Director Michael Brune, who was arrested a week earlier protesting the Keystone XL pipeline in front of the White House, said, “President Obama holds in his hand a pen and the power to deliver on his promise of hope for our children. Today, we are asking him to use that pen to reject the Keystone XL tar sands pipeline, and ensure that this dirty, dangerous, export pipeline will never be built.”

Canada was well represented by a number of indigenous leaders, including Chief Jacqueline Thomas of the Saik’uz First Nation. “The Yinka Dene Alliance of British Columbia is seeing the harm from climate change to our peoples and our waters,” said Thomas, Yinka Dene Alliance co-founder. “We see the threat of taking tar sands out of the Earth and bringing it through our territories and over our rivers. The harm being done to people in the tar sands region can no longer be Canada’s dirty secret.”

Will any of this make a difference? Even while the demonstration was underway, self-proclaimed environmentalists such as New York Times Dot Earth blogger Andrew Revkin was criticizing the demonstrators, writing that “a tight focus on Obama’s decision over the pipeline could be counterproductive if the hope is to build policies that might someday reduce the need for oil, whether the source is Alberta oil sands, the floor of the Gulf of Mexico or the Niger River delta.”

Many climate activists did not take kindly to Revkin’s comments, with journalist-turned-activist Wen Stephenson tweeting, “50,000 people come out to fight for our kids’ future, and you dump on it. You are what we’re fighting.”

Grist columnist David Roberts noted:

We can sit around and fill our blogs with reasons why this or that solution is the wrong one, inferior to some better one that we’d already have, goldarnit, if those meddling pushers-of-other-solutions weren’t ‘distracting’ from ours. We can fall in love with the ineffable intellectual tangle, as Revkin has, and accept that anything specific enough to build an activist campaign around will be meaningless in the context of global energy demand and emissions…But some people want to fight! Some people actually haul themselves out from behind their keyboards, call a bunch of friends, put on warm clothes, and go stomp around in public yelling about it.

Tensions are running high, as is often the case when so much is at stake. But is Revkin right? Is fighting Keystone the best strategic move or should we be directing our energies elsewhere? I was at the protest in D.C. and had the opportunity to speak with a number of climate activists about what lies ahead for the movement. From what I garnered from my discussions, I think Roberts has captured a sentiment that most of us have yet to fully realize, even those of us engaged in this struggle.

Yes, Keystone is a symbolic fight and stopping the pipeline will not fix our climate problem, not by a long shot. But for many people (and the numbers are rising), climate change represents one of humanity’s defining challenges, on par with the abolition of slavery, universal human rights and defeating fascism during the Second World War. It is the sine qua non issue of the 21st Century – no matter what else we might do, if we don’t get this one right, we’re in for an extremely rough ride.

This sentiment is becoming widespread in climate activist circles witnessed by, among other things, the Sierra Club’s recent decision to advocate and engage in civil disobedience for the first time in the organization’s 120-year history. The route of international negotiations and treaties has led us no closer to arresting climate change so many are now rightfully asking: If not now, when? If this is not the issue to get us out of our chairs and into the streets to fight, then what is? New pipelines represent a tangible symbol of our continuing addition to fossil fuels, locking us in to many more years of oil consumption at a time when even the International Energy Agency is telling the world that most of the world’s fossil fuels need to remain just where they are: in the ground.

Canada’s federal government is notorious for its intransigence and lack of interest in the climate change file. In the wake of the ongoing Idle No More movement and massive opposition to the proposed Northern Gateway pipeline, one wonders what climate activists in this country might be planning next. After all, Stephen Harper’s government appears hell bent on getting tar sands crude out of Alberta to international markets. If not Keystone, if not Gateway, Harper is determined to find some other way and other plans are surely in the works.

Following the protest, I had some time to visit the National Museum of African American History at the Smithsonian Institute where I came upon a quotation by the abolitionist Frederick Douglass. “Power concedes nothing without a demand. It never did and it never will.”

Whatever you may think of the campaign to stop Keystone XL, it would appear that climate change activists around the world are beginning to wake up to the cold reality of Douglass’ words. We may well look back upon last weekend’s protest as only the beginning of a long, bitter and increasingly hostile battle.