Of course, consumerism is not an unalloyed virtue. Consumerism can be utilized for hedonism. But it can also be utilized to make lives better, offering more opportunity for spiritual development. It's precisely this latter combination that the left fears, because if consumerism and virtue are allied, there is no place left for the Marxist critique of capitalism -- namely that capitalism makes people less compassionate, more selfish, and ethically meager. And so consumerism must be severed from virtue (very few leftists critique Americans' propensity for spending cash on Lady Gaga concerts) so that it can be castigated as sin more broadly.
In a world in which consumerism is the greatest of all sins, America is the greatest of all sinners, which, of course, is the point of the anti-consumerist critique from the left: to target America. Global warming represents the latest apocalyptic consequence threatened by the leftist gods for the great iniquity of buying things, developing products, and competing in the global marketplace. And America must be called to heel by the great preachers in Washington, D.C., and Hollywood.