I would be astounded if anything you said here amounted to a hate crime - it's a very, very high bar.
I suspect people here don't have a problem with the aggravated aspect of the bill. If you punch someone and you do it because they are black or transgender, it's an aggravated offence.
The one you and Rowling are concerned about is this. Rowling knew that what she posted didn't reach that bar - she doesn't actually want to be arrested and convicted for stirring up hatred. I don't think you need to worry.
OFFENCES RELATING TO STIRRING UP HATRED
(2) A person commits an offence if—
(a) the person—
(i) behaves in a threatening or abusive manner, or
(ii) communicates threatening or abusive material to another person, and
(b) either—
(i) in doing so, the person intends to stir up hatred against a group of persons based on the group being defined by reference to a characteristic mentioned in subsection (3), or
(ii) as a result, it is likely that hatred will be stirred up against such a group.
(3) The characteristics are—
(a) age,
(b) disability,
(c) religion or, in the case of a social or cultural group, perceived religious affiliation,
(d) sexual orientation,
(e) transgender identity
(f) variations in sex characteristics.
(4) It is a defence for a person charged with an offence under this section to show that the behaviour or the communication of the material was, in the particular circumstances, reasonable.