Sten wasn't berating you for being a woman fighter, that's not how the Qun see things. Rather, he was confused. Fighting is what men do. If a Qunari fights, they are a man, no matter their sex. To be a fighter but a woman is a contradiction in terms, at least to a regular Qunari like Sten rather than someone trained to interact with bas like Iron Bull.

Also remember that to the Qunari, showing another person a skill you have not mastered is deeply shameful. A big reason Sten takes so long to open up is because he isn't, from his perspective, very good at speaking the Fereldan language and does not want to use it when he does not have mastery of it.