Vegetarianism is something I've seen come up a lot lately. I have seen a lot of misconceptions about it, why it is done. Personally, I am not a vegetarian right now, although I have been in the past.
I think the first issue I saw come up was the idea that the rede says we should be vegetarians, since it says to harm none. Which, no, it doesn't - but that's something I've already addressed in the past. So the idea that Wiccans need to be vegetarians because of the rede doesn't quite hold up. And of course, it doesn't apply to all pagans, so...
Then, from the other side, I've seen people saying it's not natural for humans to be vegetarians. Well, it's not really natural for us to drive around in cars, ride roller coasters, chat online, and whatever else, but... well, we do it. Frankly, I see that sort of thing, being able to make choices, to do such "unnatural" things to be very natural for us, it's part of out nature, part of what makes us human.
I've also seen people saying our ancestors ate meat, as if this means we should. Our ancestors did a lot of crap that we would never do today. Or that our ancestors didn't have the choice. As if being a vegetarian is a new concept. Yeah, it's really not. Hinduism is a very old religion, and vegetarianism has existed within Hinduism for quite some time - as well as with other dharmic religions. Orpheus is an important figure to a lot of Hellenic pagans, many read his hymns in ritual - and he was an advocate of ending animal sacrifice, and of being vegetarian.
Beyond that, depending on where your ancestors lived, they might not have eaten very much meat at all in the first place. For a lot of folks meat would have been a rare treat, not something eaten commonly.
Like I said, I'm not a vegetarian, so I'm not trying to talk anyone else into being one. What you eat, or don't eat, is a personal choice... just don't base/justify it on incorrect assumptions.