I don't often say good things about the USPTO, so I should take the opportunity: the trademark revocation hack to pressure the change of the name of the sports team called the Redskins was a legal hack in the same caliber as copyleft. Presumably Blackhorse deserves the credit for this hack, but the USPTO showed it was sound.
Update, 2014-06-19 & 2014-06-20: A few have commented that this isn't a hack in the way copyleft is. They have not made an argument for this, only pointed that the statue prohibits racially disparaging trademarks. I thought it would be obvious why I was calling this a copyleft-ish hack, but I guess I need to explain. Copyleft uses copyright law to pursue a social good unrelated to copyright at all: it uses copyright to promote a separate social aim — the freedom of software users. Similarly, I'm strongly suspect Blackhorse doesn't care one wit about trademarks and why they exist or even that they exist. Blackhorse is using the trademark statute to put financial pressure on an institution that is doing social harm — specifically, by reversing the financial incentives of the institution bent on harm. This is analogous to the way copyleft manipulates the financial incentives of software development toward software freedom using the copyright statute. I explain more in this comment.
Fontana's comments argue that the UPSTO press release is designed to distance itself from the TTAB's decision. Fontana's point is accurate, but the TTAB is ultimately part of the USPTO. Even if some folks at the USPTO don't like the TTAB's ruling, the USPTO is actually arguing with itself, not a third party. Fontana further pointed out in turn that the TTAB is an Article I tribunal, so there can be Executive Branch “judges” who have some level of independence. Thanks to Fontana for pointing to that research; my earlier version of this post was incorrect, and I've removed the incorrect text. (Pam Chestek, BTW, was the first to point this out, but Fontana linked to the documentation.)