@TopBitchoftheWitches
I can help, sex is science, gender is made up bollocks.
Science is messy and complicated, so it’s best to steer clear of it and stick to a few slogans, such as “Sex is real.” (This one has the advantage of implying that trans people deny that sex is real, which makes them seem unreasonable.)
Don’t, whatever you do, talk to actual biologists or psychologists currently working on the subjects of sex or gender. They are obviously interested in maintaining the trans-friendly status quo, and their testimony can be ignored.
(Side note: you may have wondered whether people with intersex conditions complicate the issue. My advice? Acknowledge they exist, but in the next breath make sure to dismiss them as a negligible minority.)
Gender theory.
Just as philosophy was once said to be footnotes to Plato, so for you, all real gender theory is footnotes to Janice Raymond. You can safely dismiss developments such as intersectionality (suggested phrase: “a distraction from the real issues”), and thinkers such as Judith Butler (“bloviated postmodern nonsense”).
Mostly, of course, you can and should absolutely ignore what actual trans people have to say about their own experience. “Nothing about us without us” doesn’t apply here! You definitely shouldn’t read Julia Serano or Susan Stryker, any more than you’d listen to gay people on sexuality or Black people on racism.