all animal's right activist should also champion the cause of gender equality between men and women
Yes, they do! You will find many of the participants in Pride Parades to be AR activists.
Did you come across any animal rights activist who is not against gender bias too?
It appears that you are that person. However, there are also some in Pride parades that are very happy with gender binary and men in power.
Still waiting for you to tell us whether you think women are oppressed...