"When you throw open the doors of bathrooms and changing rooms to any man who believes or feels he's a woman - and, as I've said, gender confirmation certificates may now be granted without any need for surgery or hormones - then you open the door to any and all men who wish to come inside", wrote Rowling in her post.
"For a trans young person wanting acceptance from family members, a statement like this can give skeptical parents a reason to reject this aspect of them, thinking they will "grow out of it" because a famous person said so", Leibowitz said.
Rowling, who has received both censure and messages of support for her remarks, has yet to comment on the fan sites' statement.
She went on to make the point that many health professional are concerned that young people who are struggling with mental health issues may be pressured into taking hormones and having surgery that may not be in their best interest.
The tweet said, "Hormone prescriptions are the new anti depressants".
"Many, myself included, believe we are watching a new kind of conversion therapy for young gay people, who are being set on a lifelong path of medicalisation that may result in the loss of their fertility and/or full sexual function".
J.K. Rowling has followed up on her recent transphobic Twitter rants, conflating conversion therapy and hormone therapy.
'Pure laziness for those who would rather medicate than put in the time and effort to heal people's minds'.
"None of that may trouble you or disturb your belief in your own righteousness. But if so, I can't pretend I care much about your bad opinion of me", Rowling concludes.
"Not supporting a trans kids transition doesn't stop them from being trans".
In a series of Sunday tweets, the "Harry Potter" creator took a social media thrashing after "liking" a tweet that said hormone therapy pills were similar to antidepressants: in some cases, grossly overprescribed. "I hate how people forget that while you debate about if trans folks get to participate in public society, time continues for us", she added.
The author was previously denounced as a "TERF" - "Trans Exclusionary Radical Feminist" - for defending a woman's right to decline to describe someone who is not biologically female as a woman, and for suggesting that biological sex differences retain a degree of significance regardless of "gender identity". I know and love trans people, but erasing the concept of sex removes the ability of many to meaningfully discuss their lives. Intersex people exist and should not be forced to live in the binary.
Chiefs, Patrick Mahomes agree to 10-year extension
That means Mahomes will be in with the Chiefs until he's 36 years old, well through the prime of his career. Schefter included in follow up tweets that this 10-year deal adds on to Mahomes' current two-year contract.