For those of you unfamiliar with vegetarian death metal, I highly suggest going to check out Cattle Decapitation.
They're on Metal Blade records and have been going strong for over a decade. Social consciousness is not something normally related to genres such as death metal, and i'm sure most of their listeners still eat meat. However, it's absolutely fantastic shit. The lyrics usually deal with topics such as treating humans how we treat animals, which means like shit. They have a new record coming out next January called "The Harvest Floor" which features artwork of humans being herded into a slaughterhouse:
That makes me happy.
Cattle Decapitation interview on PETA2