You know as a bi guy I've always felt that way, but not in a " those people are jerks" way like in the quoted bit in the OP more "i just don't get it".
To me genitalia being the primary deciding factor in who someone wants to be with just does not compute.
I am always reminded by the people who unwittingly find some cute teenage crossressing guy attractive and sexy. Then after the reveal they suddenly recoil in horror and make sure that everyone knows how really heterosexual and straight they are and how they never would do it with a guy and someone with a penis, no matter how pretty and hot they are.