At any point in history, have CAs revoked certs solely to censor a target website?
Maybe the answer is yes. I don't know. But this is a rude wake-up call for me and everyone else who tried to force the world into this shape.
We've all been shouting "You have to use TLS! It's fundamental security 101. If you're not using https, your site is probably broken. And there's no reason not to do it, since it's so easy."
Surprise: Now nobdoy trusts http, and those that control https can revoke their trust based on arbitrary human morals rather than solid technical reasons.
I was a pentester for years and not once did anybody mention this threat anywhere. It's blindingly obvious in hindsight, but it was too easy not to think about it.
Let's Encrypt is in the exact same position. Why do we trust them? Think about it -- they're under US jurisdiction and subject to US laws. The government could compel them to revoke certs.
We're lucky that it's just a minor annoyance. Picture a world where no major browser renders http at all, and the only way to get a site online is to have a trusted cert.
This is not far from reality: If the Magic Leap turns out not to be vaporware, they're going to be launching a DRM-powered internet that can't be adblocked. And that means we'll all be subject to government whims far more than we'd like to admit.