The word "bitch" can mean a female dog, it can refer to the act of complaining (i.e. "stop bitching, Ron"), an annoying person-male or female ("Man, Ron sure is acting like a complaining bitch" or "Wow, that Cheryl sure knows who to be a bitch"), a frowned upon act ("Ron that sure was a bitch move to sell out your coworkers like that"). The word bitch in its versatility doesn't serve to single out one group of people; it's used to describe a lot of things.
Now tell me how has the word 'nigger' been used and how people react to "Stop being a little nigger" versus "Stop being a little bitch"? Saying the two are one in the same is trying to force PC into an affair just so you can say you waved the PC flag by comparing one word to another when it doesn't work. Grow up and stop acting like someone's word choice somehow inhibits your ability to live a normal life.