I guess I'm just clueless, but I don't see why this is so hard?
I mean, if your kid is suddenly into dinosaurs, and wants dinosaur books and little plastic dinosaurs, you get them dinosaur books and figures (within reason, of course), and maybe even take them to the natural history museum to see dinosaur fossils. And if they get bored with it after a few months, or a few years, and move on to other things, you just figure, that's how kids are, and you're glad it was dinosaur toys and not a (real!) Corvette Stingray they were whining for for six months.
So if your son (or what the doctor told you was your son) wants to wear dresses, you let him wear dresses. If he wants to wear a tutu or a spangly leotard and a tiara, you go with it. If he says "I'm a girl, call me Suzie", you go with it. And if he changes his mind after two days, or two months, or two years, you go with that, too. I cannot see how this is doing anything awful to the child. On the contrary, in doing so, you are telling him that you respect his choices and his personhood, and he gets to explore who he is in (relative) safety. And if 95% of the boys who dress as girls and/or say they want to be girls (or that they
are girls) ultimately decide that they'd rather be boys, what's the big deal about
that? (As a bonus, you'd have boys who understand that girls are just as human as they are and not some lesser form of life.)
This is pretty much the approach that, for instance, Lori Duron over at
RaisingMyRainbow.com and her fellow parents of trans and non-conforming children are taking, and it seems to work.
It seems to me that Vilain and Bailey are not really concerned with the welfare of the children they are speaking of, not even the the children who dabble in girlhood but ultimately decide to live as boys. IMHO, this is about misogyny: the idea that girl-cooties are the worst thing on earth and too close contact with them will ruin a male for life. It's also about maintaining a social structure in which man, and especially "manly" men are on top and women and girls exist mainly to be exploited and treated as objects.
ETA:
I went back and forth about which pronouns to use in the third paragraph, since I felt that almost any choice would prejudge the child's current or ultimate gender identity. I finally went with male because the assumption was that the child hadn't permanently chosen a gender, and because of the (possibly bogus) statistic that 95% of these MAAB children decide to live as males.