After further contemplation of the original post, I think I misapprehended the (albeit unarticulated) argument that lesbians should not ab initio exclude transwomen as romantic partners.
It should be a given that people have little or no control over attraction. A number of modern films (perhaps most famously, The Crying Game) present situations in which men discovered that a female to whom they were attracted and with whom they engaged in physical romance was (anatomically) male. The comical (but also tragic) result is a polar reversal of attraction. The issue(s) presented by the characters’ internal dissonance—whether intentional or inadvertent—highlights the complaints of gynephilic transwomen. In other words, if a woman experiences attraction to a transwoman only to discover that such transwoman is genetically male, the reversal or voiding of attraction signals an unstated (perhaps unrealized) hatred or distrust of men, not a question of physiochemical or physiological or psychological attraction. In such cases, the cisgender lesbian who rejects a transwoman undermines the authenticity of her expressed sexual orientation by, at least in part, manifesting a psychological aversion to men. Now, this is not to say that a homosexual ciswoman would necessarily feel attraction for a transwoman; after all, not ever heterosexual ciswoman experiences attraction toward every cisman any more than she experiences the same intensity of attraction among all those to whom is attracted. But for a person to override or suppress such attraction is conceivable prejudice.