Bisexuality came about to offer an alternative to Homosexual and Heterosexual. Homo means same, Hetero means other, and Bi meant same AND other.

Unless homosexual and heterosexual are also transphobic and inherently mean that the person is only attracted to cis-gender people, then you can make the argument that bi is as well. But they have never meant that, and to imply that they do is just wrong.

Psychologist and Human mood ring.