There is a huge problem with the way that people are taught about gender in this society. Children are indoctrinated early to believe that there are two sexes, corresponding with two genders, which are both immutable and non-voluntary and completely beyond our control. This worldview is called the gender binary, and it has no room in it for us.
Trying to teach a new perspective to the victims of this extremely aggressive brainwashing can be daunting.
I'm in the process of writing a response post to a feminist who objects to "transgender" though not to transgender people... Unlike the hateful radfems, she has an honest desire to learn and understand, which I deeply respect and so am willing to engage and put forth the effort. This very week I discovered this amazing post, which largely corresponds with what I have already written. I'll be using some of it's ideas and providing a link to it. Any more good posts on Trans 101 for Feminists/Cis Folk are appreciated!