In any case, because of this I wanted to recommend this wonderful video that concisely breaks down why these Tweets are not only ridiculous but also harmful. Jamie is trans himself and has not only made several JKR-related videos in the past discussing her transphobia, but also his entire channel is about transgender topics and issues, including his own personal experience in transitioning which is very informative for those looking to get more educated.
Another recommendation is Jessie Gender's video, "J.K. Rowling and Why Death of the Author Doesn't Work", which examines the reasons why, in the case of JKR, we can't really separate the art from the artist because her views and beliefs are placed into her works and it's unavoidable to come across something and be reminded of her particular stances on things.
On another positive note, Katie Leung, who played Cho Chang in the HP films, has recently given her opinion on this matter by openly supporting the trans community, specifically posting/linking in support of the black trans community. ❤