[irishjuggler]

So, if this person has homosexual relations with a man, does that make the man (the real one) actually heterosexual, because he is actually having sex with a woman?

Exactly. They'd BOTH actually be heterosexual. This "lesbian" has discovered that, go figure, she's really attracted to men. However, she thinks that makes her a "gay man" rather than what she actually is: a straight woman (albeit a mentally ill one).

[Scythian]

I think what it means is they’re all committing sin.