Well it is rational if you really have a preference in terms of taste. But, many people have no idea what cat or dog tastes like, but they are like "yuck" at the idea of eating dog or cat.
A couple of days back we were driving on the highway, looking for a motel. All of us were very hungry, and I was the only vegetarian in the car. We found a dead dog (hit by some vehicle) lying on the road with its flesh & blood all over the place. I commented, "Well there's your lunch". My wife (non-vegetarian) said, "well just because you don't eat non-veg, you dont have to say things like that!". I said, "Whats the problem? You love that stuff, right? If you can eat goat, then why not dog?". Grim silence.
They had goat biryani and chicken curry for lunch. Guess I will never understand.
The only real answer would be social convention.
I don't think I would start a steady diet of cats and dogs because I have been psychologically programmed not to thing of those species as food. If I ever try it I may even be so disgusted by the thought that it will effect my perception of the taste.
I have eaten horse and, apart from it tasting disgusting, I have no quams about it. But I do know that in other cultures horses are not considered as foodstuff. It is quite common to have social conventions against the consumption of certain animals and nearly all have one about consuming fellow humans.
By the way, I think this ties in nicely with the other topic about disgust as a psychological factor that influences notions of morality. In the case of meat, I wonder which one came first and created the other - the disgust or the morality?
In my case at least, I do not at all agree that it is immoral to eat meat in any way. Save animals and eat plants? Why, because plants cannot run? I don't buy that. I'm just not able to overcome the disgust. In fact I tried a lot to convert to non-veg, and gave up.
Morality is also learned, isn't it? I am not suggesting a direct correlation between morality and disgust, but isn't disgust often used as a strong deterrent to discourage people from indulging in a behavior which a system of morality decrees as wrong?
Examples: The whole incest thing. Homosexuality.