He's not against eating meat, but portions should be very low (5-10% of calories from animal products, no more, and this is a veeery small piece of meat). A (near-)vegan diet with B12- and DHA-supplements is the healthiest (DHA can be derived from algae instead of fish oil - the fish get it from algae too). An objection may be: but eating pills isn't natural. Well, eating GMO-fish surely isn't natural either.
A website with a lot of little video's about the same nutrition principles can be found here: http://nutritionfacts.org/
If the former is your belief and not the latter, please open that way.