Some people think assertive women are b****es. What you consider assertive and aggressive may differ from others. Women aren't the only ones to take a negative word and give it a positive spin, nor the first. Gay people have taken the word "queer" and made it theirs. Whether you agree with it or not, the point is, people are feeling positive and taking back their power.
I like the word b!tch as a positive word. It's strong. If someone's going to call you a b!tch because they consider it negative, but you consider those traits positive, then wear the name proudly. I have friends who proudly wear the title "slut." I have problems with the word "slut," but I'm considering my friends' point of view.
Since I consider animals above humans, being called a "female dog" is really a compliment!