Suppose someone asks: "What rational arguments can be used to validate drinking wine?"

You can survive without wine whilst still getting the nutrients you require (well, so they tell me). But so what? Wine is a great pleasure to the palate, it makes you feel deliciously intoxicated, it is a delight to share with family and friends. ("Wine is sure proof that God loves us and wants us to be happy", Benjamin Franklin.) What better reason for drinking the stuff?

Well, maybe you don't actually like good wine (shame on you!). But assuming you do, what more "validation" do you need?

Likewise, let's sit down to (say) a wonderful plate of salami, prosciutto, coppa and lardo from cinta Senese, followed by perhaps ravioli stuffed with pigeon, then a tagliatta from Val di Chiana beef ... Well, food doesn't get much better than that: it is a pleasure to the palate, it makes you feel content and deliciously replete, it is a delight to share with family and friends. What better reason for eating the stuff?

Well, maybe you don't actually like (say) good Tuscan food. Maybe you actually prefer a totally vegetarian diet (Tuscans of course will think you are quite mad). But assuming you do like that sort of carnivorous feast from time to time, on high days and holidays, what more "validation" do you need for tucking in?

But perhaps you'll say I'm just crassly missing the underlying question. Of course, on the pro side of eating meat of various kinds, there are the wonderful pleasures of the table (just as on the pro side of drinking wine, there are the pleasures of imbibing): and there's a whole wider culture bound up with husbandry and hunting. But there is a not inconsiderable con side to meat eating. In particular, there are horrible aspects of factory farming. There are the ecological arguments against using scarce resources to produce some kinds of meat.

Fine. But bringing in those considerations rather changes the issue. The original question seemed to be wondering whether there was any reason at all to put on the pro-meat-eating side of the scales. But any decent chef can supply such a reason! The revised, and more serious, question is: how do we weigh the evident pro-reasons against the con-reasons. And that different question is much disputed. An overall low meat diet, with the meat decently sourced (and rather favouring animals like sheep or wild boar raised on marginal land) is what the balance of reasons inclines me to. Others of course differ.