I've been keenly following the CG case and lurking on this thread as I have a son (my first) a few months' younger.
I remain extremely confused as to the exact facts of the case. Unless I'm missing something, we don't actually know why Charlie's parents are refusing an MRI (if they are)(?). This speculation is based on inference from the judge's words (?).
Likewise, if no one has taken an EEG since the seizures, it's unclear how GOSH can be certain about the extent of his brain damage. Likewise, no one seems wholly certain whether Charlie is in pain or is brain damaged 'beyond pain'. It is the right thing to give him prophylactic morphine - just incase.
My impression is that the situation is much less black and white than some commentary on here would suggest. I also place far less trust in NHS professionals than some commentators on here. I certainly don't think GOSH are evil, but it's wholly possible that they are - like much of the NHS - overworked and underresourced. Based on my experience of having a rare cause of infertility, I've also found the NHS to be quite conservative about what they're willing to do, and the likelihood of success. This is because, quite sensibly, there is a high bar of evidence required before public money is spent on it.
The idea of a child's welfare can be different from their best interests, and is intrinsically a conservative idea. As an example, it is not good for the welfare of anyone to go on a one way mission to Mars. Happily for future human space exploration, we permit rational adults to choose actions against their own welfare (but in their perceived best interests). I also chose actions against my own welfare - as defined by the fertility regulator - in order to try for a child, based on a gut instinct about my own poor health and reading scientific papers. This turned out to be the right decision.
Unfortunately, at the cutting edge of medicine, there's often a lack of certainty about the success of treatment, the prognosis and even the underlying physical mechanisms. It's perfectly reasonable for the parents both to question uncertainties, such as whether their son is in pain, and to ask themselves what they'd want in his position - they are his closest relations and know him best.
There are countless people with severe disabilities who campaign against assisted dying because they feel it devalues their lives. By extension, they would prefer to live than not. Hence, it is unclear whether Charlie, were he a (theoretical) nondisabled adult, would choose to risk a medical treatment with likely minor improvement rather than lose his life. First, we have no idea of his perceived experiences. Second, he may have hope that a medical breakthrough may be able to reverse his condition in the future (this is often a hope of terminally-ill adults). Unfortunately, we have no way of asking him what he wants - he is both brain damaged and a very young child.
I appreciate that some of the posters on CA are both abusive, and overemotional. However, if it was as cut-and-dried as it appears from CA -vs- Mumsnet, then I don't think the judge would be spending additional time on the case. He doesn't have any stake in making the parents feel good about themselves if the evidence is clear that they're torturing their poor son.