One of the reasons I dropped my personal Consumer Reports subscription is that they have become consistently liberal in their outlook, taking the sides of intrusive regulation by the government.
Today CR issues a statement supporting a high (62 MPG) fuel economy. One of their arguments is that vehicles can be reduced in mass without necessarily becoming less safe. For small differences in mass, this is probably true.
Importantly, reducing vehicle mass will be essential in improving fuel economy. Consumer Reports is confident that lighter vehicles will not necessarily compromise vehicle safety. For example, a contemporary family sedan such as the Hyundai Sonata weighs 3,210 pounds and still achieves a Top Safety Pick by the IIHS. It weighs 7.5% less than its previous generation and about 6% less than the average family sedan. By contrast, a Chrysler 200 weighs 3,590 pounds (also a Top-Safety Pick) but with no performance or interior room advantage. The new Honda Civic at 2,810 pounds also received a Top Safety Pick and weighs 400 pounds less (about 9%) than the Chevrolet Cruze, a direct competitor.
However, they make a big mistake here--they refer to IIHS test results between vehicles that are about 400# different. It is critically important to remember that crash test results such as IIHS and NHTSA, when they are intended to mimic front crashes, simulate a car hitting another car of the same weight.
What happens when a heavier car hits a lighter car is not pretty. Here are some great videos by IIHS which make this very point. Here is the report.
Everything else being equal, heavier cars tend to be safer than lighter cars, and forcing people into lighter cars will, on average, reduce their safety.