People seriously have issues with this? O_o I think it's a stupid thing for people to get worked up over, because it's just like Kyu said, it's exactly the same as people rping as lions, wolves, dragons, gryphons and so on. They aren't those critters in real life. Just like how we aren't the other gender of said character in real life.
I bet people wouldn't complain if you told them JK Rowling is female and wrote the roles of male characters.
Lol most of my main OCs are male, I have 7 males, and only 3 females XD (and 1 "it"/genderless).