No it doesn't. Stop being so melodramatic. It means that you do not believe that humans can change sex. Which they can't. Men need to realise that women will always see them as men, and men will always see them as men. If it is triggering, then they need to see a medical professional.
Interesting how you only discuss trans women - or "men", as you refer to them, in your post.
Gender and sex are different things and always have been. Gender is a social construct and it's mostly due to colonisation and "religious" ideals that we see it as a man/woman binary in our current world. Hugely ignorant of other cultures & history to pretend different.
Someone having a biological sex and their gender not being typically associated with that (in the modern Western view) aren't mutually exclusive.
So your saying that not affirming someone’s identity could actually lead on to major mental health problems? Do you have any evidence for this, or anyone else who backs up this claim?
Not necessarily that it will "lead on", but it can seriously amplify/trigger problems that are already there.
If someone has been through the horrifying process of conversion therapy, where they would most likely be misgendered constantly, to have someone purposefully and spitefully misgender them could trigger traumatic memories. This could lead to panic attacks or harmful coping strategies such as self harm that they use to cope with said memories. If they are already building up to it, it could be a sudden catalyst to an attempted suicide.
Similarly, body dysphoria isn't caused by misgendering. However, misgendering can, in a way "remind" someone that they are trans. Trans people don't go around their everyday lives furiously thinking "I'm he, not she, I'm he not she". Somebody suddenly calling them the incorrect pronouns might force them to become much more self-conscious/aware and bring on discomfort or dysphoria.
I think you can find many stories/accounts/anecdotes from trans people like this. I'll see if I can find any to post to this thread.
What does "accepting someone's gender identity" mean, to you?
It seems like you're saying that thinking sex and gender are different means you're transphobic? I couldn't care less what people look like or dress like, but I don't agree that it is possible to change sex by changing your appearance. I accept people's appearance and personality as who they are, but that apparently isn't enough. I must agree that this is their gender identity, which supersedes and replaces their sex.
No; the opposite, in fact. Generally thinking sex and gender are the same is a sign of transphobia.
Gender identity has nothing to do with personality/clothing. Liking pink and fashion doesn't mean you're a girl. Liking blue and sport doesn't mean you're a boy. Trans people generally try to fit into stereotypes because this just makes their life easier in a culture in which gender stereotypes are very prevalent. It can also soothe dysphoria in some ways because, like I said, gender stereotypes are hugely pervasive currently and it can help.
However, gender is what pronouns are attached to, not sex. Accepting someone's gender identity means, to me, that you understand that you will never be able to control or understand anybody else's gender, and that they are what they are. Preferred pronouns, names and titles are a way of expressing that.