A group of environmentalists sent a letter to Secretary of State John Kerry on Thursday, calling for Kerry to reject a permit critical to construction of the Keystone XL pipeline, which would shuttle thick tar sands oil from Canada to Nebraska. Fine. Their rationale? Climate change is "an even bigger mistake" than the Vietnam War, in which Kerry received multiple Purple Hearts. Bad argument.

Friday is the last day for the public to offer comment on the pipeline proposal before the State Department has to decide whether or not it should go forward. So activists on both sides are making last minute appeals. Among them, the group of activists and celebrities that made the analogy above.

The letter to Kerry, which appears in full below via the Pittsburg Defense Council, begins:

In 1971, when you were roughly our age, you asked “How can you ask a man to be the last man to die for a mistake?” The penetrating moral clarity of the question made it a turning point in the nation’s debate over the Vietnam War. ...

We stand at such a point today, with respect to an even greater challenge, an even bigger mistake – the imminent threat of catastrophic climate disruption. Your recommendation on the Keystone XL pipeline permit can help correct the course for our future, and all humanity’s.

In the grand scheme of things, failing to act against the worst effects of climate change will certainly be considered a mistake that pales nearly every other error in history. The Keystone pipeline, however, is almost certainly not the practical pivot point in that action. Global warming is a function of decades of greenhouse gas pollution, beginning at the dawn of the Industrial Revolution and accelerating as society has become more dependent on fossil fuels. We are already experiencing negative effects of warming — higher seas, deeper droughts, more precipitation. The question is how bad we let it get.

The activist group 350.org, which put an early and intense focus on the Keystone pipeline regularly calls the project the "fuse to the largest carbon bomb on the planet." The argument goes like this. We cannot add more than X amount of carbon dioxide and other greenhouse gasses to the atmosphere without triggering the worst-case models of climate science. Keystone would shuttle a fossil fuel that's essentially oil mixed with sand from Alberta to the Gulf Coast. The method of extracting and processing that tar sands oil itself produces a lot of greenhouse gas emissions — far more than normal oil drilling. (In an interview on Thursday, Senate Majority Leader Harry Reid said, "It's hard to find anything dirtier than coal. But you look around, you got tar sands — that beats it.") And if the pipeline isn't built, it's not clear that the economics of extracting in Alberta would work at all. Stop the pipeline, keep that oil — unburned — in the ground.

That oil has been in the ground since before people knew anything about oil extraction, or coal extraction, or agriculture. We've managed to get to a moment of crisis on warming without burning tar sands oil; even if we never touch a drop of tar sands oil, the amount of coal and gasoline we're burning means that there's no indication that we'll make a dent in the problem of global warming. Building Keystone would certainly make the problem worse — but it is not a John-Kerry-testifying-about-Vietnam moment.

In the Vietnam War, more than 58,000 of Kerry's peers were killed in battle. An estimated 3.8 million died overall. That war unfolded before many of the letter's signatories were born ("when you were roughly our age"). Actor Jared Leto, who signed it, was not yet born when Kerry gave his Senate testimony.

Over the course of global warming, which will lead to massive flooding and increased military conflict (like the civil war in Darfur) and food crises, millions will be displaced, injured, killed — but that's not up to Kerry right now. The reason activists have made Keystone a rallying point has as much to do with having a rallying point as anything. The movement was looking for a marquee battle and identified Keystone as the one. But it's not analogous to war. The United States cannot end Keystone as it pulled out of Vietnam and watch the problem slowly be solved. It's like asking Kerry to block the movement of a platoon toward Khe Sanh in the late 1960s, not what Kerry was actually speaking against.

Activists hope blocking Keystone will topple a political domino in the fight to stop climate change, but there's little indication it will do so. Comparing Kerry's words against the Vietnam War to the decision he now faces won't help the political fight.

Letter to John Kerry From Young Leaders