The good thing is to give browsers a way to attest to their inviolability to systems on the other end. This is generally useful! In particular, it opens up a huge potential for people to run what are effectively servers in their browsers - which was TBL's vision for the web in the first place.
The not-as-bad-as-you-think thing is that Google (and others) will use this to disable ad-blockers. Ad blockers are fundamentally dishonest, and people who use them may feel guilty for doing so. The more honest approach is to simply not consume the media. And this, it turns out, is better for society at large. Anyone who gets paid to talk ekes out a living by hacking the algorithm, making a brand, and telling people what they want to hear. It's bad and it's a bad system that makes the world worse.