Enterprise: When a great American company offers a medicine that lengthens the lives of hundreds of millions of people, you might think politicians would say thank you. Instead they say: How dare you advertise it.Pfizer has just been pressured by Congress into dropping its main ad campaign for the cholesterol-lowering drug Lipitor, arguably the most popular medicine in the world and with very good reason. Lipitor can lower the deadly artery-clogging substance by as much as 60% and, when combined with regular exercise and a low-fat diet, prevents heart attacks and sudden deaths. Companies who do so much for so...