I mean, I think what you are saying is the very thing so many people have an issue with, that if I try to say something that is definitely true, "trans women are trans women, and are in some ways different from cis women", automatically implies your second statement, "we should be allowed to discriminate against trans women because they are different." I mean, sure, some people may mean that, but one of Adichie's main beefs is that we always assume the worst in a very "if you're not with us it every way then you're against us", and that given Adichie's other actions and support for the LGBT community (no small feat in Nigeria) that she is at least somewhat deserving of the benefit of the doubt.
Otherwise what you're left with is people feeling that their only option to not be considered transphobic is if they say "trans women are women and are the same as cis women", which gets at the heart of why people are so concerned about public discourse today.
Otherwise what you're left with is people feeling that their only option to not be considered transphobic is if they say "trans women are women and are the same as cis women", which gets at the heart of why people are so concerned about public discourse today.