Whats Wrong With "B*tch"s?

Of course the word "Bitch" is an offensive word to most women and oddly some men but why exactly? If its used in the context of comparing a female to afemale dog then I see how thats extremely offensive. What if it someone says "Your a bad bitch" with a charming smile would that still be offensive? Most likely yes but its being used in a somewhat positive matter so why? Personally I call my closest of closest lady friends bitches because those are my top bitches and I have a lot of love for them and they never take it as disrespectful. Of course if a stranger calls you a bitch you have all rights to pop off on 'em. Basically I just want to know whats wrong with "bitch" and why its such a hurtful word to some ladies. If the answers dont make sense im still using that ish haha