Earlier quoted context omitted.
You can revoke your trust in any CA at any time, you don't even need to see any errors! Just click the little padlock each time you visit a secure website and see if the CA is in your good books. If it's not, pretend the padlock isn't there! OK, that's a little awkward. A browser extension could automate this. But in practice, nobody wants to do this, because hardly anyone has opinions on particular CAs. It's a sort…
Can't you just delete the CA from the browser? On Firefox it's preferences -> advanced -> certificates -> view certificates.
Users have a clear stake in whatever informational exchange occurs between them and the websites we access. We should have the authority to participate in determining the terms on which that exchange is secured.