Picking it up first and putting it in the bin? I've done this with porn and with images on cigarette cartons.
Not always possible, but just because there are problems with "real" life doesn't mean we shouldn't remove problems from online life.
Online life magnifies niches that in the offline world would be hidden away - that can be good but also means exposure to things that one is unlikely to ever be exposed to in the real world.
One can go on the web property of respected international media companies and be exposed to content that a person IRL would never share with you for fear of it ending in arrest or destruction of their public character.
I've seen far worse things online (mostly by "choice", curiosity can be a bad thing) than would ever be printed by a locally identifiable company.
Are you planning on hovering over your children 24/7 for the rest of their lives? Because you can't protect them. And ruining all of society in order to delay exposing your child to difficult things for, at best, a couple of years, is ridiculous. If you don't want your children seeing NSFL things on a computer, don't let them use a computer.
As an adult I've seen things that have screwed me up, for more than just a few days. As a child I see those things either passing one by or being far more severe; both options are open depending on the particular nature of the content.
> If you don't want your children seeing NSFL things on a computer, don't let them use a computer. //
So people should only use computers if they want their children to see NSFL things?
There are alternatives top that position.
Personally with my [pre-teen] children I allow them to use computers with whitelist settings or with direct oversight - this in response to access to porn with our eldest child.
In physical daily life people would laugh at you for claiming that I'm a helicopter parent - I've been "told off" in public a couple of times for letting kids "too much freedom", but once they're wise to roads, sensible with new people, aware they can be injured then they're pretty safe around the general population as a group. Online you don't have the public available to help, children don't have their normal senses of danger and wariness that they build up from bumps, scrapes and bruises.
For sure, as teenagers they'll chase after "interesting" content both of a sexual and gore-ish (and ...) nature out of curiosity, but I'm not going to abandon them to that in the same way I'm not going to drop them off to play in a crack house.
The attempt to equivalise published porn that you saw as a child I'm guessing >15 years ago [?] with the crudest of online content available now is damaging. I too saw porn as a child of a similar age, softcore images of airbrushed men/women, and wouldn't shirk at my kids seeing the same; it's not like they don't know what naked people look like. NSFL content available online, both porn/gore/other, is an entirely different category and warrants a completely different approach to 'normal' sexual imagery IMO.
And what's to prevent the same sort of "mentally broken" person who would host a website with NSFL images, from simply printing them off and dropping pages on the street? How were you planning on preventing your child from picking up a piece of paper on a street corner with NSFL images?
We all want to protect our children from the "real world" for as long as possible. But at some point they need to learn to cope with the fact that this world is full of disgusting people and actions.