"Transgenderism" bothers me too, particularly as it's used in the ISO(?) Standards. My endo lists that as my official diagnosis, but it sounds more like a life choice or a philosophy than a medical conditional. It trivializes us. As to "transgenders" as a noun, I was never really offended by the use of conditions as a noun when it was from the outside, "mentally ill" as opposed to "people with a mental illness", but I was conditioned against using it in my training. Now, from the inside, I get it.