Hahaha, complete dipshit. I love that sentence. Idiot must live in a hole or something.
I'm not vegetarian but the only non-fish meat I eat right now is chicken, and if I had the money I'd go for that free range stuff too. Cows and stuff have almost identical biology to us except for their brain size, they can suffer and be sad just like the animal homo sapien can.
As for the diet, eat egg whites twice per day (50g protein), (and if you start eating fish, which I'm pretty sure don't suffer too much...) tuna (~35g per can), salmon (another 30g), whey PWO (50g), casein at night (another ~50g). That's about 215g protein right there, without even including nuts, soy, beans, protein from veggies/grains, etc. Most salmon has almost no mercury, and chunk light tuna is also pretty low. So you could easily get healthy and buff, probably not super huge, which as you said you do not want.
Here's a vegetarian:
http://scoobysworkshop.com/aboutme.htm
(although he only converted a few years ago)