Oh, Virginia, as far as I heard and understood, it is - though widely used - rather insulting and discriminating for women (referring to their too often very low status in society), in most compositions and circumstances, and that since long, in spite of the original definition, i.e. the female canid.
And, in many languages, calling someone a dog (for males) is an insult; further, you have the expression "underdog" (shaming losers, victims, preys, weak, inapt, poor and miserable people).
http://www.thefreedictionary.com/underdog
So, I'd rather avoid to use it; I sinned often out of ignorance - there were and still are all the "false friends", as, before on-line access to the flood of present day information, vocabularies were often very incomplete (as definitions and translations were limited and, partly, incomplete or not giving the correct sense, in pocket sized books) and good dictionaries cumbersome and rather expensive, while the different domains required branch specific terms and jargons.
The Virginian is on my too long bucket list; it is one of the cases, in which I saw three or four TV episodes (with James Drury and a much nicer Trampas, played by regretted Doug McLure) before having had the occasion to read the book or get at least some more information about the story and the author. And besides Owen Wister, there's also Zane Grey, Louis L'Amour, etc.
