I genuinely do have trouble unifying my instinct that nazi propaganda, for example, should be censored, against my understanding that what constitutes "solicitation to commit crimes" is relative to what a society considers "good" or "bad," which is (somewhat) arbitrary.

Take your list as an example. Any action that is damaging to the State could be considered Criminal - perhaps something as simple as developing good cryptography, for example. Some things are crimes that shouldn't be - smoking marijuana, an example. Simply saying "solicitations to commit crimes should be censored" thus doesn't jive with me.