Lin545: I want to know if Swiss people do so and how they justify it.
My guess? The Swiss don't care if you eat dog or cat or not, similar to how Americans don't really care if you eat roadkill or not. The laws against selling it are probably due to the inability to check the conditions of the animal before slaughter, not the consumption per se.
Could it have been an earlier tradition? Depends on what access to meat they had, other than dogs and/or cats. In Crete, traditional Christmas meat is pig, since the pig was usually slaughtered in December, then the whole meat of it was prepared in various ways to last the year (smoked, cured, vats of oil and fat, sausages etc). In areas where pigs were not common, a different animal could have been substituted for the traditional Christmas meal (turkey comes to mind). So having a cat or dog for Christmas, if that was the only available animal one could slaughter, would make sense.