Mate you're not reading with both eyes. He did not deny their 'right to feel' in whatever ways they want.
Doctors are used to actual, biological mutations, not psychological.
He specifically wrote that he wouldn't do that. He would not deliberately offend them. What more do you want?
We as a more or less rational society can treat people politely, but that won't change their issue which is a psychological problem. They will get offended and feel shitty all their life, not because people are bad, but because they suffer from severe mental delusion.
Deluded people are not a threat to society per se, but they can and they will if granted to much power.
Hence it is important to keep the distinction in mind.
What if it's not psychological only, though ? While there are trans that do it for the reasons you imply and do it for the wrong reason, not every person changing gender does it for the same reasons. And some have medical conditions that explain the changes in the way they feel or react to things. You're aware that being heterosexual, homosexual, bi, etc. isn't only psychological as well, right ? There are lots of other factors including pheromones, hormones and such.
For instance, take mtf trans people. Some of them might have had issues with their hormones resulting in higher testosterone levels, having more hair growth even beards, and displaying typical masculine attributes and thus could feel like they are more masculine than feminine...and it's not "psychological". It's what their body is telling them and making them react to. A male to female person could very well be attracted to males after transitioning too, as those 2 aren't mutually exclusive...but they'd still feel better in an external shell that ressemble the internal workings of said shell.
The problem here really is people not trying to understand something that they aren't familiar with and rejecting the issue by saying "they're mentally deranged".
For instance, when i was younger, i was under the assumption that being homosexual was a choice (mostly because you were kinda taught so and we didn't have as much exposure to them as we do now). I've since then understood that, while it can be the case sometimes, it most often isn't and that sometimes in the way a human baby is created some things are different...It's not only about XX or XY. It's not black or white. Just the same as how everyone has a different pain sensibility, is attracted to different odors or persons, etc.
It's not about them being unique snowflakes but allowing others to live their lives as they see fit as long as it doesn't impact yours.
Edit: yes, i understand better now. Indeed, the people doing it because of hype and/or because they think it'll solve their problems are only going to get disappointed and bitter. But it's hard to not speak about both groups since they both underwent the same changes, not for the same reasons. And i think harming one group harms the other.