I don't know if you've been paying attention, but the folks denying science/facts/reality have been the global warming deniers who don't want any fuel economy standards.
What makes you think Obama has something against diesels?
Anthropogenic Global Warming is a hoax.
The planet has been on a cooling trend since 1998 as actually observed by the Jason satellite (jointly run by NASA and the French).
C02 is not a pollutant.
The most significant spike in atmospheric C02 we can determine preceded a little period called the ice age.
Another recent major increase in global carbon dioxide levels occured in the period from 1940 to the mid seventies, which occurred during a cooling trend.
The UN IPCC "hockey stick" chart that is largely responsible for this hysteria has been proven to be flawed by actual climatologists. Even taken at face value it only indicates a 1.1 degree change in mean temperature over the last one hundred and fifty years. Hardly a planet killer.
Global warming is not fact or science; it is merely a religion for the irreligious. It requires faith in the unobservable, and accepts no challenges to it's stated authority. If Global Warming Cultists cared about the environment, they would seek the "best" solution to potential problems and amiably discuss all viable alternatives. Instead, we are given dire warnings and told how to live regardless of the consequences. AGW fanatics don't give two rips about the planet, they (you) care about telling me what to do. You sir, may place that where the sun doesn't shine.
I don't know about the President in particular, but his supporters and sycophantic followers are part and parcel of wrong headed anti-diesel policy. From what I observe of the man, he probably hasn't the foggiest notion how an internal combustion engine even works much less the difference in fuel types. That type of thing doesn't matter to him - only the big squishy Marxist utopia vision he is working towards.
Don't take my word for it - look into the reasons behind the recently cancelled light duty GM and Ford pickup diesel, environmental policy compliance. The final surrender of VW to TDI models across the lineup was also based on wrong headed enviro-policy from left leaning state governments blocking their every move.
No one challenging the AGW hoax has said they don't support better MPG. It is just that instantly jacking CAFE standards while restricting efficient short term methods of getting there is a piss poor (and very likely economically catastrophic) method of solving a non-existant at best problem.