Here's what Unicef says:
> Pornographic content can harm children. Exposure to pornography at a young age may lead to poor mental health, sexism and objectification, sexual violence, and other negative outcomes. ...
> UNICEF is alarmed by the massive quantity of pornography available online, including increasingly graphic and extreme content that is easily accessible to children of all ages. Efforts to regulate content and restrict children’s access to pornography have not kept pace with technological shifts that have profoundly altered the landscape for the consumption of pornography.
(At least I'm not aware of any public libraries with adult-only sections.)
And in the context of the overall discussion of a bill attempting to restrict specifically children's (not adults') access to porn.
But since you asked, I'll respond. I have my own computer and internet connection, so I don't watch anything at the library. But it's not unheard of for homeless people to watch porn at the library.
This simplistic line of 'porn bad' is just the pretense for labeling anything out of line with your religion's prescribed morality as pornohrafic and therefore worthy of being expunged by violent means. This ideology never stops at videos containing nudity or sex but continues on to being directed at music, literature, women who don't cover their heads, Transgender people, and so on.
It's the exact justification currently used by conservative turbo-karens to ban books from public libraries that contain any trace if LGBTQIA+ content, histories that acknowledge the slave trade and racism, or even basic health information about periods.