Why do they need defense? From whom? Well, this Newsweek writer thinks vegetarians are sanctimonious and they sneak corn-dogs when nobody's looking. From the other side, vegetarians are attacked by vegans for not giving up dairy and eggs as well as meat. To add to a vegetarian's woes, some of the famous ones are reverting to meat-eating. I was not at all happy to read that Mollie Katzen, author of my very favorite vegetarian cookbook, has a recipe for beef stew in her newest cookbook. (I recently looked at the three books of hers I own and realized she was probably never an animal-concerned vegetarian to begin with. Oh. Well.)
Since I take the vegan perspective most seriously, of all these perspectives, I'm just going to defend vegetarians from attacks that could come from that direction. Note: just could. I think lots of vegans are sane people who aren't looking to attack anybody.
So--let's start with vegetarianism in a traditional, idyllic world. You live in a village in the Swiss alps, where the views of the mountain tops are as pretty as can be. Your cow Bessie lives happily in your field while her domestic partner pulls a plow. There are hens and roosters in your yard. By milking Bessie and taking eggs from the hens, you are able to enjoy the delicious vegetarian food in Mollie's cookbooks. Is there a moral problem there?
Tom Regan is the philosopher who put "yes" on the map in his 1983 book The Case for Animal Rights. Regan says that even in the idyllic scenario, you'd be violating the basic rights of an animal to be treated with respect. By using these animals as resources (getting work from the bull and and resources from the cow and chickens), you are treating them as means, obviously without their consent.
I'm on board with the notion that animals should be treated with respect, whether or not we add "rights" talk to the mix. However, I don't share Regan's sense that the animals on Idyllic Swiss Farm are treated disrespectfully. So I don't in fact think there's a problem there. Vegetarianism is all that's required of anyone in that setting, and not veganism. Which goes to show: there's no absolute or universal prohibition against using animals for food or other purposes.
But now jump to your own real situation. Sad to say, you probably don't have a view of the alps out your window. You don't have a cow in your yard or any chickens. The animals that produce your eggs and milk are in fact treated with disrespect. This is glaringly true if they come from factory farms, but still true if they come from "improved" factory farms or even humane farms (which are never as idyllic as Idyllic Swiss Farm). Barring any special circumstances, you will stop eating eggs and milk if you are in the finest moral fettle.
The thing is, most of us are not in the finest moral fettle. We recycle, but not everything. We see that driving and flying produces carbon emissions, but at most we cut back. We don't stop. We can see that buying luxuries for ourselves is vastly worse than contributing to Oxfam and thereby saving lives, but we still buy some luxuries. Most of us are not, in short, moral saints. So when we decide how to behave, we think in terms of priorities. You recycle the big stuff, but not every scrap of plastic. You get a smaller car, but not no car.
So the question (for us sinners) is whether a vegetarian diet is based on a rational set of priorities. And...guess what?...it is. Just think about eating chicken vs. eggs. If you eat chicken all year, the cost in chicken lives is 25-50. All those chickens will have endured what chickens go through to wind up on our plates--which is a lot if they were ordinary factory farmed chickens, though less, if they weren't. If you eat eggs all year, roughly one laying hen went through those same things, plus one male chick was killed (since the males have no economic value). That makes it a very rational choice to give up chicken first before eggs.
If you think through the costs to animals and the environment of beef vs. milk, you will come to the same conclusion. Ideally, we should give up both. If you're not up to that, then your first priority should be giving up beef.
Even when people desperately want to change their diets for the sake of their own health and appearance, they very often don't succeed. It's even harder when the issue is not your own well being, but the treatment of other creatures. I think vegetarianism is a rational half-way house for people not ready to go completely vegan. It's a choice that stems from knowledge about animal products, not from ignorance.
Then again, is it really important to choose a rational half-way house as opposed to just some half-way house? Be a vegan before 6 pm, says Mark Bittman. Even Gary Francione approves of Vegan Mondays! I think vegetarianism makes much more sense than these possibilities, but I'm all for any way of cutting back on using animals for food. All of these options reduce the number of animals being mistreated, and that simply has to be good.