I know how you feel I have a bunch of "brothers" too. I'm sure they think of you as a sister too, they were probably just kidding around. If it's really bothering you, you should talk to them.
Oh and by the way, LOVE your icon! Yay Death Note! (:
I don't really understand how that could be taken as a low blow. All they asked was for you to stop saying dirty things. That doesn't mean that they're viewing you as a girl they can't have. If a girl is going to say dirty things around a guy, they'll end up getting turned on. It just seems to me like they were simply trying to avoid that.