Also, its a bag made from dead animals, the genders of which we do not know. Therefore, I don't think there is any such thing as a 'manbag' or 'girlbag'. Do what feels best. Since when did the act of carrying things become a girl exclusive phenomenon? Check the last 100 years. New Century, new people, new generation, new style, new rules.
If you're gay carry it with some beefy attitude. If you're straight carry it with some dandy panache. Style is about balance and ambiguity. Marc Jacobs, (who happens to create this LoVely stuff that is like crack for my senses), carries a birkin as well as Neverfulls, etc. Do you think Marc would have gotten to where he is as the Creative Director for the most successful luxury brand in the world if he had listened when people told him not to carry a 'girl bag?' Certainly not. And we're all thankful that he didn't listen, or else so much of the creative synergy of art and fashion in the LV brand would not be possible under the supervision of anybody less.
Sorry for the long post, but I gotta get on my Marc Jacobs High Horse every now and then. Viva Marc y Louis.