There is an overabundance of rational reasons to say no to factory-farmed meat: It is the No. 1 cause of global warming, it systematically forces tens of billions of animals to suffer in ways that would be illegal if they were dogs, it is a decisive factor in the development of swine and avian flus, and so on.
I often think about how my sons will come to know about September 11th. Something overheard? A newspaper image? In school? I would prefer that they learn about it from my wife and me, in a deliberate and safe way. But it's hard to imagine ever feeling ready to broach the subject without some impetus.