I don't have a problem with increased mpg, increased power, etc. All good.
What I DO have a problem with is the government mandating stupid stuff (and practically trying to legislate physics while they are at it). Let the market decide. If people want little fuel-efficient cars, manufacturers will make them. If they want powerful cars, they'll make those. They want trucks? They'll make those. And since there is a wide variety of what people want, they make a wide variety of vehicles, which is great. Throwing mandated mpg requirements in there will result in stifling the market in the long haul. And all for what? Making a couple people feel better about themselves?
Government trying to force and manipulate markets and technology rarely ends well.