"There's an old stereotype about black people not shutting up in a movie theater. There's a lot of truth to it, but it's not just black people, and it's not just in movie theaters."
That seems like a strangely incendiary way of saying there's a lot of people who don't know when to be quiet....
I wish you did not repeat racist stereotypes thinking that that would help to make your point. It doesn't. It just makes you sound racist.
'Library Rules' also include things like "you're only allowed to be on the computers for 15 minutes" and "Storytime is at 2pm". Libraries have changed over the years.
I can say from experience in many libraries that not everyone understands library rules. There's an old stereotype about black people not shutting up in a movie theater. There's a lot of truth to it, but it's not just black people, and it's not just in movie theaters.
And then there are the libraries, growing in number over time, that have simply abandoned the ideal of silence. Most libraries still ban loud talking, cell phone use, music, etc. but now some of them tolerate it and some even encourage it. Some of these noisy libraries designate a quiet area, but it tends to feel like an anachronistic throwback, designed to mollify the people who aren't coming to the library just to hang out.
I think in the future the phrase "library rules" will not mean what you might think, if it still means anything at all.