I know of only 3 different languages - arabic, english and burmese.
In each of those languages "dog" can be used as an insult towards another person. "You fucking dog" is oddly enough, a phrase used in my own society to denote a traitor or someone that is morally corrupt. To call a person a "fucking cat" however would not carry any sort of derogatory connotations, rather it would be a laughable try at an insult.
I have also however noted that "dog" is also a term that is used in Arabic and Burmese to insult another person. For instance, in burmese "kwih"(dog) when sworn at another person is used to suggest that the person is uncivilized, filthy and having no virtue or honor. The same is true AFAIK in Arabic.
Its particularly strange to me that "dog" can be used as an insult in the west since our society tends to place a pretty high status for dogs - i.e man's best friend. How did the word "dog" evolve into an insult? Why "dog" in particular as opposed to other domesticated animals like cats or birds?
Follow up to this: how about "bitch" and words like it in other languages for female dogs becoming such a ubiquitous insult in so many cultures and places across time? It seems like "son of a bitch/hijo de puta" is fairly common as well.
As a follow-up, do 'dog' and 'dawg' have the same origins? One may be derogatory, while the other isn't.