To add to what Pfhreak says: no, identity can be more nuanced than that (identities can change, and identity only as a negative may not even make sense in non-b

To add to what Pfhreak says: no, identity can be more nuanced than that (identities can change, and identity only as a negative may not even make sense in non-binary contexts), but the easiest way I find to address the issue to (presumably) cis people is to address particular identities in terms of being perceieved as the opposite, because that can highlight the discomfort of self- and other-identity mismatching.