But Citizens United doesn't rely on a broad interpretation of freedom of speech at all. It relies on a broad interpretation of freedom of association. Supporting various political views is "speech" by any possible understanding -- that's not broad at all. The main "innovation" of Citizens United is that when people form associations (like corporations) they retain certain rights, such as freedom of speech.
A better analogy would be if we already all agreed that individuals have the right to send encrypted messages, and we were discussing whether corporations retained the same rights. Then you'd have a point, bringing up Citizens United. But when discussing whether people have some underlying right at all, it doesn't seem relevant.
Of course, people will point to X law or precedent and say "see that justifies it'. They don't see how that law should be invalid by the very logic that the state created for itself.
Would the Citizens United case apply hear? I'm thinking about corporate personhood arguments.
https://en.wikipedia.org/wiki/Chilling_effect
The term chilling effect has been in use in the United States since as early as 1950.[8] The United States Supreme Court first refers to the "chilling effect" in the context of the United States Constitution in Wieman v. Updegraff in 1952.[9]
It would be like federally outlawing clothes to make sure no one in America has a gun. Also, and aside from the whole premise being unconstitutional, shallow, & generally kind of silly, enforcement would be just about impossible.
Different judges are looking at it in different ways. I say assume they can search it or hold you in contempt for the password if they intercept or find it. Then, you shift the goal post to them not being able to do that.
EDIT: I wholeheartedly disagree with restricting E2E and believe in freedom of speech as strongly as one can believe in any explicitly enumerated right, I just don't agree the text of the First Amendment covers this, and it's hard for me to imagine any of SCOTUS coming up with an argument supporting it.