As a FTM, I don't find there to be any specific endorsement of body views in the article. Rather, he is being transparent with who he has in mind, which is extremely helpful to someone like myself. It lets me know how to approach the text for my own use.
I think immediately dismissing the author as harmful merely because he's exacting in his disclaimers is a disappointing take. If it isn't applicable to you, that's fine. Going so far as to lob accusations over body image is pretty rough - more so when you're not the target audience. Finding good sources speaking to the FTM experience is so rare and it saddens me to see anyone want to tear it down right out of the gate.
Why would it be a mistake? If you want to have blue hair, go for it. Life is short and dyed hair is for everyone.
I'd like to see the results if you feel like posting it!