Turn the narrative around.
Ask why he's so homophobic and supports 'transing away the gay'? The prevalence of same sex attracted teenage girls who have been drawn to transition raises huge questions about what's going on. Where have all the teen lesbians gone? Then add in the element of sterilisation.
Why does he think it's ok for males to tell lesbians that they are transphobic for refusing to do dick? Are women supposed to change their sexuality to accommodate the feelings of men? That sounds a lot like conversation.
The evidence used to support transition is from mainly males. There has been a desire to lump everyone who identifies as trans as a singular group. Yet when you look at this dispassionately there's a problem - it's mainly older males who transition and very young women and girls. And that's just the start of the differences. The treatment needed to transition is totally different for each sex. They literally give each group a totally different set of drugs. So why do we lump all research together? We don't actually have a body of evidence for female transition at all. What we do have is knowledge that the drugs used for female transition have particularly bad side effects for other conditions. Yet this is just hand waved away because all trans people are the same.
There's no proven clinical benefit to transition. No one has found that transition actually is improving quality of life and reducing mental health distress. We know that distress is persisting despite transition. So how is it actually helping to transition?
People who identify as trans deserve high quality care and research. We know this isn't happening. Especially not for minors where information about outcomes hasn't even been recorded. How is this ok?
You can't make an informed decision to transition in the absence of this. It's just all ideology and belief based.
Talk about how we know that the comorbidity issues are leading to transition being seen as a fix all because fear of being accused of transphobic is preventing proper support and care for other underlying issues which don't go away if you transition.
Then ask why the burden is on women to prove that there isn't an elevated risk to them rather than on trans people to disprove the risk. Keeping in mind we know that transition in sex offenders is HIGHER than the general population by quite some amount.
Ask why women aren't allowed to define themselves and why they must accept the definition imposed on them. And our language to describe ourselves is being removed but this isn't mirrored with the word man. Isn't this sexist?
Why are transwomen not safe from male violence in the mens? How are women safe from male violence in the women's if males have full access.
Ask how can the laws on voyeurism be enforced if any male can claim to be female and enter a female changing area without question. Any woman who challenges risks being assaulted or accused of transphobia.
Ask how the impact of males using female facilities is being measured. What is the rate of self exclusion? How is this being recorded and measured to ensure that groups such as Muslim women aren't being disproportionately disadvantaged. Ask how he is ensuring that cultural concerns aren't leading to women being told by men that they must not participate in activities they previously would outside the house? If this isn't being recorded to ensure that harm isn't being done to the lives of women, why isn't it being recorded?
Ask why it's known by aid agencies that access to single sex toilets vastly reduces the rate of sexual offences committed and it is always recommended in disaster and development projects that single sex provision is essential to women? And why the same thing no longer seems to apply to the developed world? Isn't it racist to suggest that we are somehow more civilised? Where is the evidence to back up that mixed sex / gender neutral provision doesn't lead to an increase in sexual violence following this known pattern elsewhere in the world? Isn't it sexist to fail to check this?
Then we have the whole debacle the Edinburgh rape crisis centre raises. Why are traumatised women asked to reframe their trauma by a man who isn't qualified in counselling and doesn't even have a GRC and applied for a job designated as for women only and backed up by legal exclusions that allow for single sex applications? How does he justify putting the identity of staff members ahead of traumatised, vulnerable women? Should women be refused care in this situation? Should they be forced to accept males to do intimate examinations because they identify as women?
I'm sorry you raised a sexist, homophobic, racist son. And even more sorry that he's too pig headed and arrogant to listen to his mother and her life experience. Where does he get off dismissing you. Why is he so ageist?
Everyone knows what a woman is. They are the one who gave birth to you.
Men know who women are because they know which ones to oppress. And abuse.