No, the person is right. It's realy fucked up to eat and kill another sentient beeing to feed yourself, if your could just as easy not do so.
So you think grass and cows are comparable here? I'd be careful to judge others people's intelligence if I where you.
Here is an article that shows some contra points to the theorie, in case you want to have a look at that too.
The evidence for it is rather shallow, realy.