Alcohol (Ethanol) is made from food products (primarily).
Creating a fuel source that competes with a food source for resources drives up the cost of foodstuffs (not just the items themselves, but the farmland and labor resources for farming the source as well)... this can have severe catastrophic impact for those barely making ends meet as it is.
At the beginning of US Ethanol usage the price of tortillas in Mexico skyrocketed 400% as the US grain supply that was previously shipped there was diverted to make fuel. This led to riots and protests, as well as families going hungry.
Unless people start eating hemp, there shouldn't be a problem. I made the same point in a comment. The competition between ethanol producers and livestock farmers has driven the cost of pork and beef up... That's why hemp is the best alternative.
People do eat hemp. The seeds are pretty nutritionally superior to a lot of other grains. I hear it makes decent brownies, too. The milk sucks though.
It still needs land, cultivation, etc.... less workers/acres being used for food crops (food farmers switching over to the new "cash crop" specifically) drives up food prices as well as using the food itself as fuel. I know everyone wants hemp to be some miracle problem solver so that it can be legal and they can smoke it whenever they want... but it's just not. Not saying it should be illegal... it shouldn't... just saying always trying to find "reasons" to validate its legality only muddies the waters of the issue.