I have to research this topic a little better, what I am about to say. But I am pretty sure that, let's just say, most of what follows is true. The 14th Amendment talks about equal protection, due process, and privileges and immunities. I actually heard a lawyer on TV once say that we all have the right to freedom of speech as privilege and immunities. That is not correct. The phrase "privileges and immunities" first appears in Article IV, Section 2 of the main body of the Constitution, where it refers to the rights you have as a citizen of your state. The 14th Amendment protects the rights you have by virtue of your U.S citizenship alone. The right to vote being the most often cited. So, the state of California could extent the right to vote to illegal immigrants. But it doesn't have to, according to the Supreme Court. But even illegal immigrants, as a protected class under "equal protection", would always have First Amendment free speech rights. Of course, under common law, as soon as you are convicted of a felony, they can start taking all your rights away (except the right against cruel and usual punishment, I think). The right to vote. And your Fourth Amendment right against search and seizure, if they want, when you're on parole, for example. Now I've never heard of a state taking away someone's First Amendment rights, like speech or religion, for conviction of a felony. I think that is because of what my Law Dictionary by Steven Gifis calls the doctrine of "Preferred Rights" in cases like Murdock v. Pennsylvania (1943), it says, means they never can take away First Amendment rights. Every amendment below the first, is fair game, I think. Anyone here who is a lawyer? Why do they never seem to be able to take away people's First Amendment rights? Not even if they're serving life in prison. It's because they never can, right?
I’m going to go out on a limb with a guess that case law has allowed those other rights to be limited so as to ensure the safety of the community at large, and that with regards to free speech, there’s no further demonstrable call for limiting this right for an ex-offender above and beyond the restrictions already deemed appropriate for the citizenry at large.