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