Ethanol will not reduce smog and produces 22% more hydrocarbons than gasoline resulting in higher ozone levels that can cause respiratory problems.
Source: Scientific American April 2007.
Also why divert valuable fertile farmland from food production to ethanol production. We have plenty of oil and gas that can be used to power vehicles.
No problem banning diesel powered automobiles. Period.  The concept of bio diesel is misleading suggesting that bio diesel is cleaner than ordinary diesel.