Your central point, that it's a collective action problem, is Heath's main point, as I read his article. He points out that people do not live environmentalist lifestyles as evidence that they will not vote for making non-environmentalist lifestyles expensive, and thus Klein's claim that democracy and local politics will help solve this issue is fundamentally mistaken.

And assume they use a lot of gas because they have ATVs. Which makes no sense at all. The mileage on those is actually not terrible, and they are typically not driven very long distances. Those motorcycles are even better than cars on fuel consumption.

While I agree that he doesn't have sufficient information to conclude the amount of gas they use, it's certainly fair to claim that their lifestyle is fossil fuel intensive, which was his claim. I have friends with guns; the amount of gunpowder consumption they require is better measured by how frequently they go to the range, not the number of guns they own. But it still seems fair to argue that using guns is a gunpowder-intensive hobby.

Even if everyone did it, the price of gas and coal would just go down, and other countries would buy it

...other countries don't count as everyone?