What arguements can I give?
Well, I can tell you my own arguments for not eating meat which I usually tell people when they ask me why I'm a vegetarian, some of them are already excellently spelled out by Sevenseas;
If we make a distinction between humans and animals, then we as humans have a responsibility that far exceeds that of animals for the welfare of our planet. Why? Because this responsibility is beyond morality, it also deals with the ethical treatment of other species, including our own. We have rules and regulations to govern our conduct, animals do not - but if we do not then try to be morally and ethically obliged towards every living thing in our vicinity, what differentiates us from "them" (i.e. animals)?. We have evolved as a species, we have technology, religion, culture etc. - and our actions are based on reason and logic (well, most of the time anyway) - if we were to act as animals - i.e. act based on instinct, then we might as well throw "civilization" as a concept out the window and go live in the wild as animals. Since we can / will not, then we have to act as humans and not as animals. As Sevenseas said; animals are not morally responsible for their actions, but we are, and just because you CAN do something, does not automatically give you the RIGHT to do it."We were meant to eat meat, we're part of the food chain, evolution got us where we are."
Not to repeat what Sevenseas said, but again the following I feel is a very, very indisputable strong point; we have evolved to the point where meat is not necessary for survival. Before "civilization" as we know it, humans ate meat because of necessity, but now that necessity is no longer there, I, for one, am an example of a person who have never eaten meat in my life (thanks to my parents) and my whole family are more healthy individuals than most of the families I know around me.
- but laying aside these things, ask them if they can tell you what is "normal" about mass-produced meat. What is normal of having a conveyer belt of cows, pigs, chickens slaughtered for the pleasure of our palates? Since it's no longer a necessity, then it must be only based on the fact that it "tastes good", i.e. purely based on egotistical reasons and pleasure, but not everything that is based on the pleasure-principle makes it right! And just because you CAN do it, doesn't mean you have to, or that it's right to do it. What if you were a serial-killer and derived pleasure from slaughtering people. Society would condemn your actions immediately, saying it's "wrong" - however, if you were so inclined, would you do it just because you could? Even if you know that you were doing something wrong, based on ethics and morale?
Let me say this, I for one, would have a lot less problems with people who went into the wild and caught their own dinner, than those stacking up burgers and hot-dogs at your local supermarket. If everyone went hunting, had to catch their own meat and / or kill and prepare it, 99% of the humans on earth would be vegetarians, if not vegans (the rest of the 1% would be redneck idiots who already survive by catching their food). If anything, this mass-slaughter of animals is just wrong, based on the fact that there's nothing "normal" or "necessary" about it!