I dispute much of what you claim, that 9lbs isn't going to waste, it's going to make meat.
Take for example corn vs beef. Beef has 10x the protein, you'd have to eat 10x as much corn anyway.
I like meat more than some of the feedstock grains.
http://ndb.nal.usda.gov/ndb/foods/show/2926
http://ndb.nal.usda.gov/ndb/foods/show/3853
What qualifies a Geography prof on ethics? Did he minor in philosophy? I'm under no illusion that, in general, any particular diet is ethically superior to others.
In my corn/beef example there isn't even a very strong efficiency arguement to be made.
Next time you make your list of dead, white, male, vegetarians, of historical importance add Hitler to the list.
Now for ethics, do you live in a house? Did you disturb the natural environment to build your shelter, provide food and other necessities? Do your recreational activities further displace animals and cause environmental degradation?
Of course they do.
One could argue, by your logic, your larger than necessary environmental footprint isn't ethical either, and I'd bet your lifestyle does more damage than the incremental impact of my meat consumption.