Exactly. It's even worse than the belief that privacy is unnecessary unless you have something to hide, since it enslaves you to a positive obligation to informing others, and despite the risks. If you have something interesting to say regarding humans, then you have to judge that there doesn't exist someone sufficiently threatened by it to do you or your interests any harm, and thinking through that is both stressful and uncertain. The safest default assumption is privacy.

Just getting some of your thoughts down in writing is a first step, like a diary or journal. Maybe a few of those thoughts should be public soon, or maybe not. But getting them down helps your thinking and is useful.

Writing is not a public good by default, but merely a physical manifestation of thought, and thus private.