Whatever your reasons, I don't like to be preached to.
But it must have some impact, religion uses it pretty effectively - heck, sometimes it even changes people's behaviour. (more of persuasion-design another day)
So whilst it's easy to cringe a little at the Americanism of this 6 minute TED. He makes the point clearly, life's not about absolutes; but it is about choice. And as a society we could do worse than make a few simple, responsible decisions.
Think about what you eat, think about our impact and stop being greedy bastards Monday - Friday at least.
Whatever your reasons, feel free to drop the slogan, the essence kinda makes sense.