Common arguments by Anti-Trans folks:
The correct response is “A woman is someone who identifies as a woman”.
Sometimes, people reject this statement and claim it's a circular definition and not valid.
However, it isn't a circular definition, because of use-mention distinction in philosophy:
A woman (use case) is someone who identifies as a woman (mention case)
Some say sex is based on the gametes someone produces. However, there's people who do not produce them.
The counter-argument is that that someone should be male or female, based on what their body “should do”.
Bodies are not teleological however, are aren't “meant” to produce female or male gametes. They just are. There are people who produce both gametes too.
Thus, sex is not binary, and there isn't a way to group people into “man” and “woman”.
https://kim-hipwell.medium.com/why-gamete-production-does-not-define-sex-ae80eb67c379
Not true. And it's up to a person to decide if they want to use the label transgender.
Trans people have already been using the bathroom!. Transgender people existed for centuries.
Security guard kicked cis-women out of bathroom, as he thought she wasn't a women https://web.archive.org/web/20250506170851/https://www.theguardian.com/us-news/2025/may/06/boston-hotel-bathroom-same-sex-couple
No evidence was found that trans women using bathroom increases safety concerns.
More importantly, studies have reported trans and non-binary youth are at higher risk for sexual assault when not using the bathroom they identify with.
https://williamsinstitute.law.ucla.edu/wp-content/uploads/Trans-Bathroom-Access-Feb-2025.pdf
This is a known as a Slippery Slope fallacy (https://www.youtube.com/watch?v=Qt4f7QrfRRc).
This is unrelated to addressing a person's preferred gender and name.
If you run the argument backwards to as “not allow”, then you can run into a bad conclusion too. While the argument is valid form, it's not sound.