I think what buboard is talking about is that CAs can revoke certificates that they've issued, and can refuse to issue certificates to particular sites. Someone might pressure CAs to do this for a content censorship purpose, much in the way that people pressure other kinds of intermediaries and technical infrastructure providers when they find some online site or content or activity objectionable.
SSL depends on national agencies and orgs overseen by national agencies.
If SSL is required, then whoever controls those agencies controls what's seen online.
I already cannot easily add a root CA for .onion addresses and then make my own certs there, without browsers screaming bloody murder.
I already cannot bypass cert errors for certain types of cert fails.
Tor onion sites, which are end to end encrypted, are considered "insecure" because we plebes cannot buy a "proper" EV ssl cert, like Facebook did.
Enforcement of SSL is just another way of controlling the user in name of "stupidity". Sure, the dumb click-anything users win, but anyone tech-savy loses freedoms.
Looking forward to it. I imagine, when SSL becomes mandatory by browsers, it can be used for censorship.