Gender identity is a construct and only part of what makes a successful pairing. Most important are compatible genitals - meaning genitals compatible with the interests of both parties. I am a cis man interested in other cis men. Cis erasure is no more acceptable than trans erasure; as a gay cis man I am not interested in vaginas no matter who has one and I shouldn't have to argue the point. It does not validate trans people to invalidate cis people, it just creates further division.