One of the largest problems that I have ever had with the word bitch as an insult is that it is quite unfair to female dogs.
The word bitch, when used to describe a woman, means someone who is mean, judgemental, cold and uncaring. This is quite unfair to real bitches, since all the female dogs I have ever known were kind, accepting, warm and concerned. Of course, there are many angry guard dogs that are female, but in the realm of personal, not business relationships, female dogs are not "bitches".
Bitch is often applied to a man when he is weak, untrustworthy and underhanded. Again, dogs are usually strong, loyal and straightforward.
Thus, calling someone a bitch should really be used as a compliment.