The Christian Vegetarian Association is a great organization that advocates a vegetarian diet based on Christianity principles of love. There values seem to be so true on why one should be vegetarian:

for health

for animals

for reasons dealing with the poor and hungry

for being caretakers of the earth

About the Christian Vegetarian Association:

The Christian Vegetarian Association (CVA) is an international, non-denominational ministry of believers dedicated to respectfully promoting healthy, Christ-centered and God-honoring living among Christians.

We advocate nutritious plant-based diets in the global Christian community. Through publications, websites, and related public information campaigns, we educate people about the distinct health, environmental, and animal-related advantages of plant-based eating.

http://www.all-creatures.org/cva/vegbenefits.htm

http://www.jesusveg.com/christiantext.html

This article sums up many reasons on why many Christians choose to be vegetarian (similar to the Christian Vegetarian Association reasons)

for peace and nonviolence

to help end world hunger

to help protect the environment

for health

to support human rights

Everytime an omnivore asks why you are vegetarian, or if you get enough protein, or if you eat enough, etc, refer them to this article!

Finally, another great resource is:

http://www.all-creatures.org

Check it out!