Biology as in “this is what I am (or was born to be)” and psychology as in “this is what I do (or am tempted to do).” One is identity, the other is behaviour. There is no sin in the former.
At least according to my understanding, there’s also no sin in someone saying “I’m a man who is sexually attracted to other men” (i.e. “I’m gay”) or “I’m a man who is sexually attracted to both men and women” (i.e. “I’m bisexual”). And the church in it’s documents on homosexuality sometimes seems to be talking about what people are, not just what they do. So, when the Church issues something called, “Letter to the Bishops of the Church on the Pastoral Care of Homosexual Persons,” it sounds to me as if they’re talking about what someone is (i.e. they’re a “homosexual person”), not just what they do. This, it seems to me is just another way of saying that someone is gay.
When someone says they’re gay or bisexual, they’re just stating one of many facts about themselves like, “I’m American” or “I’m an optimist” (as opposed to someone who by their nature tends to be pessimistic), or “I’m a bibliophile.” When someone says, “I’m a bibliophile,” they’re not talking about an action but about something intrinsic to themselves, the fact that they love books, they love to read them, they love to look at beautifully printed or illustrated books, they love the feel of a book in their hands, etc.
A drunk is admitting his behaviour, not his biology, in AA meetings, otherwise he could not work the 12 steps, which requires seeking forgiveness.
When someone says, “I’m an alcoholic,” they’re not just saying that the last 100 times they had a drink of alcohol, they couldn’t stop drinking. They’re not just talking about actions in the past. They’re saying that if they have a drink next week or next year, they won’t be able to stop drinking before they’re drunk and therefore, they can’t ever drink alcohol because not being able to drink in moderation is an intrinsic part of who they are. They’re an alcoholic. Unfortunately, because it’s considered by some people to be shameful to say that they’re an alcoholic and that’s just the way they are, they refuse to admit to themselves that they have a problem drinking alcohol and that’s just a fact about themselves that they need to recognize.
Sure our genetics influence our behaviour and some of us are tempted to some things more than others because of our nature. But what is the motive for identifying ourselves with destructive tendencies? To what extent should we label ourselves with our weaknesses and faults? This is also borrowing language and norms from a culture that promotes perversion, so that confuses things.
The only reason I can think of for why a person should be against someone saying that they’re gay or bisexual is if
being gay or bisexual is something shameful that should be concealed.