Why would you expect them to do anything? Racism is one of the least vile things of the vile things that Tor makes possible, and it isn't even illegal.

(Edit: Wording slightly changed to reflect point raised below.)

Tor does not support any vile things. It's a freedom platform. A tool. Honor is not in the blade but in the hand that holds it.

To make it clear that they dislike the fact that their work is being used in this way, but, as the article states, that they are technically unable to do anything about it without completely compromising the entire reason Tor exists.

Or so people stop emailing them asking what they're going to do.

By design, there's pretty much nothing the Tor project can do about what people use Tor for. (Beyond publicly repudiating it.)

If they could, the whole idea wouldn't work.

They addressed that in the article. They can't do anything.

they make anonymity software