J.K. Rowling is certainly not far-right. I’m pretty sure that the creators of South Park are more right-wing than she is, and even they have been making fun of the alt-right in recent years.
No, I don’t think J.K. Rowling is justified when it comes to trans issues. However, the responses she’s been getting for it aren’t doing anyone any favors. All it’s really accomplished is making her look like a victim. She’s less likely to see the error of her ways if her detractors are threatening her. If people want to show Rowling how ignorant she’s being, threatening her and calling her a female dog are not the ways to go about it. Criticizing her is fine, but you have to remember that she’s still human at the end of the day.