To add onto the hippocratic oath argument: gender dysphoria is a devastating mental illness, and so far the only effective treatment is transitioning. Conversion camps don't work, and there isn't yet a "cure-all" drug that would make dysphoria go away. That would make a case for artificially induced PMS to be less harmful overall than gender dysphoria.

As for the "we were all female once" argument, that shouldn't really matter. Neuroscience is a complicated field and it should be of no surprise to anyone that there can be a gender-sex mismatch at birth. The only reason we even see these issues is because humans culturally separate themselves by gender on a society level. There are probably trans animals out there but we wouldn't know because they wouldn't care. Also, two of the three trans people I personally know are trans men, people often forget transition goes both ways.