There are two reasons why I love JKR. (Actually, there are LOADS of reasons I love JKR, but let's just stick with two.)
One is that whenever she intervenes on issues like this, she always demonstrates that she is much cleverer and funnier than the hapless male idiot she's arguing with. You almost feel sorry for them, because it's not a fair fight - but then Jonathan Liew doesn't believe in fair fights, so sympathy is limited.
The other is that her comments always get picked up by the press. If she hadn't said anything, this would have been a massive Twitter spat, and nothing more. But as soon as she said something, you knew it would be reported in the Mail, Telegraph etc. I assume this is because JKR makes good copy, and people will always click on a story that has JKR in it. Probably does wonders for the publication's SEO too.