Disclaimer: I don't personally think animal welfare matters, so I'm playing devil's advocate here. The views of people who actually do care about animal welfare may differ. (I do believe there are other good reasons to reduce meat consumption, but that's a separate matter.)
Robin's claim that pretty much the same amount of land will be devoted to farming regardless of demand for meat seems unjustified, given (a) the massive scale of deforestation going on to make way for livestock, and (b) the generally higher yield of plant crops. (Nick's point about animals being fed plant crops is relevant here too.) In addition to the carbon impact (the UN estimates that such deforestation accounts for 6% of global GHG emissions) this means that, contra Robin, demand for meat is likely to result in animal deaths.
That said, I think Robin is still correct to argue that the main impact of reducing meat consumption will not be to save animal lives, but rather to result in fewer animals being reared. The question then becomes whether the lives of such animals are so bad that they're not worth living. Robin asserts that they're not that bad, without really arguing for the conclusion. People have written books detailing how bad the lives of factory farmed animals are, and I buy their story more than Robin's lack of story.
It nonetheless seems plausible that the lives of non-factory-farmed animals are worth living, despite their eventually being killed for food. I agree with Robin that this would make eating them OK from the perspective of animal welfare.* However, in contrast to Robin, I don't think that we're making the world a better place by bringing them into existence.
* Which is to say, OK if you ignore the environmental costs.
Well argued conchis! The fact that you have been so thoughtful throughout this discussion makes me quite curious why you don't think animal welfare matters.
I think it does (somewhat) and the points you make against Robin were the same ones that jumped to my mind.
One minor additional point, I hope that reducing my consumption of animals and raising public awareness and concern about animal suffering, will result in the creation of a larger market for "humanely" raised and slaughtered animals.
I have noticed that among philosophers, vegetarianism of one form or another is quite common. In fact, I became a vegetarian (technically a pescetarian) myself partly out of respect for an undergraduate philosophy professor. I am interested in finding out if there is a similar disproportion in the Less Wrong community.
I didn't request that this go into Yvain's survey because I want more information than just what animal products you do or don't eat; I'd also like to see nuances of the reasons behind your diet. There are a lot more shades than carnivore/vegetarian/vegan - if you want to be a vegetarian but are allergic to soy and gluten, that's a compelling reason to diversify protein sources, for instance. I'd also like to hear about if you avoid any plant foods (if you think they're farmed in a way that's environmentally destructive or that hurts people or if you have warm fuzzy feelings for plants, maybe). Here are some questions that come to mind: