
As far as vehicles and user perception go, the Hummer generates strong feelings, both from owners and non-owners. I recall reading an interesting article in the NYTimes about the gap in perception that arises between the Hummers owners and everyone else when forced to share the road.
“Hummer loyalists come across as a beleaguered lot…Hummer drivers position their ownership at the center of a ‘brand-mediated moral conflict’ in which Hummer enthusiasts are not only innocent but also heroic. Conflict with vehement critics turns out to play a key role, with the Hummer owner casting himself or herself as a ‘moral protagonist’who must, according to this theory, ‘defend sacrosanct virtues and ideals from the transgressive actions of an immoral adversary.’ And what sacrosanct virtues would those be? To oversimplify a bit: American exceptionalism, rugged individualism, love of the frontier, community and freedom.”
Indeed!
Below is a chart from Forrester illustrating segments and percentages of the population willing to adopt green solutions. I think we would be safe to say that owners of the Hummers would be in 44% segment of non-green users.

Changing attitudes towards sustainability when it conflicts with consumers values and perceptions, such as the Hummer owners, would be considered a downright Sisyphean task.
So how can this reluctant segment of the population change? The motivation would have to be externally driven, versus internally generated. As the hypothetical owner of a Hummer, I might not care about the carbon footprint of my vehicle but I might drive less if gas prices go sky high again, which would make an impact considering the Hummer’s poor gas mileage (estimated to be 9 mpg).
Another external driver that might drive change in behaviour would be government intervention. Due to a loophole, Hummer owners in the US can get a tax-write off of up to $100,000 as a business expense. Removing the unfair loop hole can change behaviour towards selecting a more sustainable choice. In addition, due to weight classifications, the Hummer and other large SUVs are exempt from meeting any emission standards. A simple reversal of this absurdly unfair rule can do a lot to motivate owners, and potential owners, to switch to a more sustainable vehicle.
Note that these sort of external drivers would also work with the other segments of the population that is more amenable to green solutions as well. With the exception of the early adopters, the push to use sustainable solutions and products usually are harnessed with another factor such as economics (cheaper to use this green detergent) or efficiency/usability.

