Some people put vegetarian references in their signatures, including quotes from famous people.
Some example quotes are below. Whenever people say 'We mustn't be sentimental,' you can take it they are about to do something cruel. And if they add 'We must be realistic,' they mean they are going to make money out of it. There must be other, less cruel ways of obtaining knowledge. The lower animals, like man, manifestly feel pleasure and pain, happiness, and misery.