I am very very pro organ donation and am on the register myself, but I think this is wrong and agree it is poles apart.
I'm not seeing it as stopping life support being a decision to actively kill the foetus. I am seeing it that every attempt they are making to keep the woman's body going is consciously choosing to give life to this foetus. If it was already or very close to being viable that would be a different case; it is not.
Just as you wouldn't create a test tube baby and implant it into a dead woman's womb, I think this is wrong; I believe that consciously extending "life" of this woman's body is the same thing. We (as in humans, scientists, doctors, whatever) simply don't know enough about what we are doing. Organ donation is different - we have been doing it for a long time and know that it doesn't have any unwanted effects (like you always get in films e.g. the donor's personality somehow imprinting on the recipient). I don't know by the way if organ donation was experimental at first, but in any case, it's naive at best - it's basically assuming that all a baby needs to develop is a placenta and nutrients. But we're discovering new things about babies all the time, what they are aware of in the womb. It wasn't just the things about the baby being unable to hear normal sounds of life (we now know that language development begins in the womb), a heartbeat (presence of a mother's heartbeat after birth in kangaroo care stabilises an infant's heartbeat and breathing more effectively than any incubator), feel the normal movement of the mother walking around (there are theories around sensory development which hinge on movement such as this, again, we just don't know how important this is yet), but those were things that made me think - what else are we missing, what else don't we know? Is she kept warm? If not, what implications would that have, considering that the body is "expected" to be warm?
And what we do know - from other cases - the Texas case, where the baby did not develop properly. We don't know what we are doing. That is reckless in the extreme. It's not "doing whatever they can to have a chance of saving the baby", it's grotesque. This is nothing but a human experiment. And to the person who said "Of course you wouldn't tell the child!" - What, and this child (if it miraculously did survive to be a healthy person) isn't ever going to turn into an adult and find out?!
I think future generations will look back at what doctors have done in these cases and be absolutely horrified. I think there will be massive implications, probably which we won't realise for a long time because I think it's likely that the baby will die or be born very disabled.
When we develop the means to gestate babies outside of a woman's womb then this will be possible, for now, we should leave well alone. We can already "gestate" 20 week + foetuses fairly successfully - that ought to be the cut off point here too. And I might add that although incubator care is pretty well researched and well known now, we still wouldn't attempt to keep a 34 week pregnant brain dead woman alive, a c-section would be performed and the baby would be cared for by incubator. Because we know what we're doing with incubators.