It seems the point they are trying to make is that for (wrong, according to them) reasons, a person's internal gender perception is privileged over other types

It seems the point they are trying to make is that for (wrong, according to them) reasons, a person's internal gender perception is privileged over other types of internal identity, such as the false belief that one is the messiah or Napoleon, or one has missing limbs. It's an interesting enough point, which deserves careful thought, although perhaps this is not exactly the right forum for it. Also, note that they did say in their comment that the correct pronoun to use when talking to Manning was 'her', which seems like being nice to others, and respecting their choices. I'm guessing it's probably considered unhelpful to reinforce delusions such as believing oneself to be Jesus, but would be interested to know where psychiatrists draw the line in such things.