Nope, I can see why she did that.

First off, this topic attracts the Wrong People as well. By the Wrong People I mean terrifying crazy people who will never leave you alone, not merely people with wrong opinions.

Second: she's a woman in science on Twitter. The appalling sexist hate she will absolutely trigger by simply speaking up warrants at least throwing the switch so it can't be seen. This is why so many women writing for newspapers now ask for the comments to be switched off on their articles, too. Because it is endless and soul-damaging.