Yes, we should aim for zero emissions. Yes, the health impacts carry their own costs not to mention the human tragedy. However, good public policy is about rewarding good behavior (eg. tax credits) and punishing bad behavior (eg. tax, enforcement, penalties). Everyone loves to talk about the latter, while the former is ignored.
We really need to be long-term smart about how we craft environmental policy in America, and particularly so given other countries unwillingness to manage pollution in an effective or transparent manner.