Vegetarians and Christianity

The other day in class, a friend of mine was talking with me about how he's a vegetarian, and that he thinks everyone should be because it's cruel to eat animals. He asked me what I thought about it, and I told him that I am a Christian, and therefore believe what the Bible says about God giving us animals for our benefit(or something to that effect, I can't remember the verse right off the bat). He then said that the verse that talks about that, in the original Greek, the word doesn't mean rule, that we can make them do what we want them to, but more council, or guide. That we have in fact enslaved animals, and to eat them is cruel. Now I obviously don't see his point of view, but if what he said is true, and that we are supposed to be more a guide, and than a ruler, then could it conceivably be wrong to eat meat? I know animals aren't people, and therefore don't have rights like we do, but there must be a reason why we don't eat certain animals right? Or is it just a matter of culture? Like do they eat dogs and cats in other countries?and if so, is it a sin? I don't know, just something I was thinking about.