It's a woman. The backlash in part indicates why a regeneration in female form, or perhaps more to the point why stories with female leads, need to happen on our screens. The dominant narrative we have been telling ourselves in the west is that, as in Ancient Rome, the young white educated man is the pinnacle of human being, and anyone else of different age, race, colour, creed, gender, is somewhat sub-human. That is not acceptable.
It's not a man. Someone commented that The Doctor is a male lead who challenges some dominant narratives about what it is to be a man. I agree. The Doctor prefers non-violence. The Doctor finds beauty in difference; his response whenever he encounters a species he's not seen before is 'Oh, you are beautiful!' The Doctor may appear - and appear to think he is - a lone figure, solitary, alone, but he is not. The Doctor collaborates, with people (and others) different to him, and the women in the story are very often cleverer, stronger, even kinder, than The Doctor. So we lose something with a regeneration into a female Doctor, something worth naming and celebrating from Doctors 1 to 12.
It's a woman. It is worth noting The Doctor's consistent affirmation of women and not only in recent storylines anticipating this regeneration. This regeneration is not inconsistent with The Doctor's character. It is, however, a story the show could not tell before now.
It's not a person of colour. Fair point. Another part of that dominant narrative is the whiteness of it. Here I may risk negating any argument in favour of a female Doctor. Can - and should - this story, this character, be all things to and for all viewers? As many have pointed out in comments, Doctor Who has been, especially in the current era, remarkable in its presentation of characters of diversity. I could cite only 10's adventure on the Titanic and the prejudices of the rich and pretty towards the poorer, larger couple; the prejudice Banakafalata feels as a cyborg; and the inherent prejudices about education represented in the guide's story. Companions have expressed all kinds of sexualities, and included the wonderfully platonic relationship between Donna and The Doctor, for me a welcome antidote to the Doctor-Rose dynamic I thought was a bit over the top. The companions are not 'support' roles as subordinate characters; they drive the story along with The Doctor, and gain the interest and love of viewers just as much. The diversity that has already been present in that wonder-filled blue box cannot be underestimated, and must be acknowledged and celebrated. I don't think The Doctor can be all the things; but Doctor Who has presented the glorious diversity of humanity in a way that makes diversity seem natural, the norm, the opposite of the posturing and denigration of 'other' we see in some responses to #Doctor13.
It's a woman. And Jodie Whittaker is a human being of dignity and worth and to be anything other than kind to her is to go against the very ethos of The Doctor you claim to love.
It's a woman. So is Missy, and a fabulous, obvious, regeneration of The Master she was.
It's a woman. What an opportunity, artistically, to explore unexplored areas of The Doctor's character and story. Yes, it is an opportunity politically as well: we are clearly much further from equality, from the respect and affirmation of humans because they are humans than The Doctor is.
It's a woman. Get over it. No one is forcing you to watch. I am looking forward to it, more than I thought I would. The reveal got me, convinced me in 60 seconds. She is The Doctor, and I can't wait to watch her stories.