That's a freaking load of crap. His argument tends to lean toward:-
1) teeth structure of humans :- Humans have canine teeth, that's because of our evolution from monkeys. What will be his answer to "lion has four legs, why don't we use our arms to crawl then?"? or that lion tiger etc. drink water by a very peculiar movement of their tongue, while humans more or less gulp?
He totally circumvents the question of animals are "masoom" and should not be eaten. His argument is you can eat "halaal, animals who have four legs" because it's permitted by Quraan, well then why discriminate against Elephant?
2) Other argument being "total protein", our body does not require all the proteins that are there in the world. Vegetables have adequate protein required by the body to function properly. What one vegetable lacks can be provided by other set of vegetable, you won't remain protein deficient with a combination of two three vegetables. Milk has complete proteins, someone tell this preacher.
I hate these kind of preachers playing to the lobby. Idiot skipped the total essence of the question and choose the relevant portions to suit his arguments. This is how ignorance spreads in society. Atleast give proper knowledge if you want to justify meat-eating habits.