This is disturbing and depressing. As one of comment posters in the Telegraph article wrote, eating dogs and cats are not common among the Chinese, and certainly most overseas Chinese consider that barbaric. In many of the large cities in China, the people treat pets the same way as most Westerners do.
Yeah, I think that many westerners assume that eating cats and dogs is common in Asian countries, even though it is uncommon. It may happen, yet not as often as westerners would like to think (I say 'would like to think', because I've seen many rednecks who get a kick out of thinking that most Chinese eat cats and dogs).
In regard to the question about why eat cows and not dogs or cats; well, in Vajrayana a skillful practitioner should be able to transform any substance, and—about animals in this regard—create a positive cause for the animal in the future (i.e. by eating animal flesh with presence, or better yet Instant Presence, creates a karmic connection to the Dharma for that animal).
Now I do think that it would be best if non-practitioners were vegetarian; and, if everyone were vegetarian, there would be no killing of animals which would be even better. However as long as animals are getting killed, then practitioners should help the already-killed animals by creating a positive cause for them; however that, again, eating meat ought to be discouraged among non-practitioners, unless there are health reasons for eating meat for some individuals (Tibetan Medicine explains the benefits of eating certain types of flesh for various health conditions).
Speaking of which (back to the point I was getting to), since Tibetan Medicine does explain the benefits of eating certain types of flesh for various health conditions, there are specific reasons why eating some flesh is beneficial, while eating other types of flesh is usually non-beneficial or even unhealthy. Like I said, a skillful Vajrayana practitioner is said to be able to transform any type of flesh; yet for the average-joe, eating meat like cat, dog, and many other carnivores is often quite unhealthy, whereas eating other types of meat can help to balance the humours, etc. Although I do think that there are conditions where eating carnivore flesh can help to balance the humours as well, however in most cases carnivore meat is unhealthy; and if one is vegetarian, then in many cases there are probably herbs and other dietary guidelines that would suffice.