The fact they think you have of been born with your physical sex as a female in order to roleplay a women highlights several things to me.

1. They are no true roleplayer's (And I say this having quit forum RP'ing myself several years ago)
>They proved they are unable/un-capable to roleplay as certain character's due to their sex

2. They are rather one dimensional character at that
->Seeing as they seem to think a character's sex is such a big deal that it alone determines how and who can roleplay them.

3. They're close minded and bigoted assholes, therefore unworthy of your time
->If they do not accept you simply because you identify differently than they do then they live a very narrow, hateful and limited life. One you gain no benefit by being part of or allowing to take influence over your own life.