From The Straight Dope:
Ban small cars? Don't be ridiculous, CAFE advocates say. We'd all be safer and use less gas to boot if we banned SUVs. A 2002 study of 84 cars, trucks, SUVs, and minivans conducted for the U.S. Department of Energy concluded that SUVs and pickup trucks had the highest combined risk of any vehicles — that is, risk to both their occupants and occupants of other cars. True, the average SUV protected its occupants better than the average small car. However, some midsize cars protected their occupants just as well as SUVs without unduly endangering the occupants of other vehicles. The study also found that the safest compact and subcompact cars were as safe for their drivers as the average SUV, and safer from a combined-risk standpoint.
Research I had read about several years ago, but have never been able to track down again when I needed it until now. Tell your SUV driving friends.
And there is also the issue of higher insurance rates, partly due to the fact that if, for example, you strike a little old lady in a sub-compact you might break a few of their bones. Whereas if you hit them with an SUV, they tend to squash.