In addition to what the other person said about broad vs specific, content neutrality.
If you punch anyone who talks loudly, that's problematic for other reasons but not censorship per se. If you punch anyone who talks about Tienanmen square, you're censoring them.
Pornography would be an example of something the US censors in certain contexts. We aren't banning your billboard because it's a billboard, we are banning it because the image on the billboard is people having sex.
But if you only make sure anyone who talks about Tienanmen square from ever holding job again that is fine, according to the people who keep saying the freedom of speech is not freedom from consequences.
If you punch anyone who talks loudly, that's problematic for other reasons but not censorship per se. If you punch anyone who talks about Tienanmen square, you're censoring them.
Pornography would be an example of something the US censors in certain contexts. We aren't banning your billboard because it's a billboard, we are banning it because the image on the billboard is people having sex.