Just because there's no objectively correct measure, I wouldn't say that means it isn't wrong. There's nothing objective in ethics.
In your example of people not caring about their health: the environmental impact of diet is in a different ethical class for me. If you choose to ignore your own health that's your deal, but if you make choices that negatively impact the lives of millions I think the ethics are different.
In your example of people not caring about their health: the environmental impact of diet is in a different ethical class for me. If you choose to ignore your own health that's your deal, but if you make choices that negatively impact the lives of millions I think the ethics are different.