1. It depends on what you’re referring to. Sex and gender are two different things. “Biology” is unfortunately a common talking point for transphobes who inexorably link the two, so it immediately makes lots of people doubt a good-faith conversation. Transphobes like to use “biology” to try to prove that sex and gender are hard binaries. In reality, biology is all kinds of messy. But that’s an entirely different tangent. From a biological sex perspective, it would (likely) be factually correct. They have XY chromosomes, were AMAB, etc… (Not every trans woman will fit that description, because of situations like intersex people who don’t fit into nice neat little male/female checkboxes. Again, biology is messy and imprecise. But for the purpose of this conversation, I think we can agree that it is generally correct.) But again, transphobes will often try to pounce on that to falsely exclaim that you believe trans women are really men.
2. Not really, because of the whole “gender isn’t sex” thing. Biologically speaking, they could be a half-male-crab-half-female-porcupine abomination for all I care. It still wouldn’t affect their gender, and I still wouldn’t give a fuck which restroom they used.
3. I think I just did. Biology doesn’t determine gender. Simply make sure to cover the whole “gender isn’t sex” thing, to stave off the transphobes who think I’m agreeing with them. In reality, the best response is usually a half-hearted “yeah, so?” Because the people making statements like this usually aren’t doing so in good faith. At best, they’re sorely uneducated about sex, gender, society’s effect on the two, etc… And at worst they’re trying to bait an argument or set up some kind of gotcha moment. Sometimes the best response is to simply not take the bait, because we have better things to spend our time on.
4. Because gender isn’t sex. Trans women are women, because genetics or hormones don’t determine your gender. Someone can simultaneously be both biologically male and identify as a woman. It’s not a zero-sum game where one negates or overrules the other, because they’re not linked.

In addition to what others have said, I’d like to add a little more information.

Hormones work by changing your gene expression. Every one of us has all the DNA for both typically male and typically female traits. Hormones play a part in deciding what parts of your DNA are active within your cells and what parts aren’t. There’s a complicated set of interactions that decides what hormones you produce naturally and how your body responds to them. Sometimes something happens in an atypical way with that complex set of interactions and that’s how intersex people exist.

(There are examples of people with XY chromosomes who have internal testes but are insensitive to testosterone and grow up female, and even examples of people with XY chromosomes who have functioning uteruses and have given birth naturally. It can get very complicated)

When you go on HRT as part of a medical transition, the instructions your cells are following in your DNA switch to the instructions tied to those hormones. That’s how trans people’s bodies change. Their cells are actually functioning differently.

A trans women on estrogen for a long enough time will eventually have their blood proteins go to a more typically female profile. They’ll also see their risk factor for certain diseases switch. The risk of cardiovascular disease goes down (typically something that affects more males) and their risk for autoimmune disease go up (typically something that affects more females).

So are trans woman biologically men? Eh, not quite. Saying somebody is biologically male/female is a little reductive. It can be complicated.

isn’t that the point?

You should base your response on the basis of civil liberties: a trans persons’ preferred identity should accepted because they’re within their right to do so. We, in return, should respect their decision.

1: Yes.

2: Not really. It’s more about self image and social presentation.

3: Best response I have is, “And?” Covers a lot of bases.

4: Same way you get any title like Doctor, or Fam, you need to be accepted into the community by peers, and not necessarily universally.

who cares

if someone asks to be called she/her/susan then just do it. it doesn’t need to be so complicated

conservatives ranting about biology are attacking a straw man. nobody actually gives a shit

(My opinion)

1. Yes it is factually correct, but it’s not an argument
2. maybe matters (what bathroom do they use I have no idea)
3. I would say they are correct but it doesn’t prove anything about trans people being invalid (trans people are valid af, having the courage to change your gender is something I couldn’t imagine)
4. There is a difference between gender and sex. Sex is your biology, gender is what you identify as. Your sex can be male while your gender being female.

I want to be clear I’m not queer this is just what I have learnt in school (crazy our school actually teaches us about this), I could be wrong.

Why respond to it. If someone’s already recognised someone as a trans woman what’s the problem

Aight, you asked multiple questions, so you’re going to get some strange answers, possibly including this one.

To your title question, the only time I’ve heard anyone say that, they were being a douche. My response online is mostly of the “down vote, report if appropriate, and move on” variety.

In meat space, my response is usually either an eye roll and walking off, or a “fucking moron” and walking off.

I have big dude privilege in meat space, and roll well armed, so have no need to pretend to be nice to douche nozzles spewing bullshit.

The other questions are harder.

1: for a given value of factual, sure, I guess. But it’s using imprecise language that’s been weaponized, so I would be dubious of someone stating it until there was more context. “Biological” isn’t as definitive and limited in usages as to be without question in that context.

2: don’t matter. If a guy says he’s a guy, he’s a guy. If a gal says she’s a gal, she’s a gal. End of fucking story, and I will gladly tell anyone fucking with my trans homies that they’re a fucking moron and be willing to either walk off, or fuck them up if they insist. IDGAF about sometimes XY or XX status, or any of the other possible combinations (remember when I said “Biological” isn’t that useful or definitive? Yeah, biology ain’t a binary). I care about the person’s expressed self. It’s about basic human decency and respect.

3: I wouldn’t respond logically. It doesn’t merit any effort on my part. I’m not in the business of convincing anyone that everyone has human rights, should have equal acces to all civil rights, or that someone else’s gender is none of their fucking business. It isn’t about logic. Anyone at this point trying to frame gender as some kind of science debate is a douche and can go fuck themselves. The debate at this point has nothing to do with “biology”. It’s about human rights. And yes, I will fight on that hill.

4: it would only contradict if the person trying to bring “biology” into a conversation is being a douche instead of just missing the point. I don’t automatically assume a person trying to frame the subject in those terms is acting with malice. So they may not be contradicting the fact that trans women are women. They may just be exploring the language of transness in an attempt to better understand the matter. And that’s okay. It isn’t a built in part of language, so everyone has to absorb the concepts over time.

Alas, assholes and morons use that language to denigrate trans people. So I also can’t assume someone isn’t doing so. I have to wait for context, or be proactive in stating that I ain’t putting up with bigotry, so if that’s where they’re going, it won’t end well.

Me? The debate is over. What’s still in play is people finding their path to internalizing the subject. We don’t get to debate what is a fundamental human experience. Trans people exist. It isn’t imaginary on their part, it isn’t bad parenting, it isn’t trauma. They’re trans, and that’s it.

My answer: if we’re sat the point that you don’t even understand the definitions of sex, gender and sexuality I don’t think we have the time to discuss this. Ultimately, regardless of definitions, we should treat humans as humans and be kind to one another.

In general, please don’t ask loaded, third-rail questions on !asklemmy@lemmy.ml, because

1. it’s a PITA for mods, and
2. that’s not what the community is for:. It’s supposed to be a clone of r/askreddit.

It’s extremely hairy messy to define biological sex. Whoever wants to argue has a middle school level understanding of biology, refuse to learn and completely ignores the science.

See

Why do I have to have an opinion? Why can’t we just let them be.

I feel like it doesn’t really warrant a response, but the statement is true nonetheless.

“You’re biologically a loser lmao”