I'm not of the opinion that we should just let kids see that stuff, though at the same time Im skeptical that it's as bad as some people claim, but I just don't see a way to actually stop them from seeing it that isn't way worse than the status quo via restricting everyone else. If the cure is worse than the disease, then one isn't advocating that the disease isn't harmful by rejecting the cure, just stating that the trade-off is not worth it.

As far as giving kids a dangerously wrong idea of what sex is goes, I do think that the best solution to this is better sex-ed than trying to hide things from them though. The thing about porn is that it isn't really possible to stop, without getting insanely draconian. You might be able to stop most kids from being able to access popular websites for it, sure, but given all the stories I've heard from before the internet was popular about people as kids finding relatives nsfw magazines and video tapes, that won't stop a curious kid, just make it slightly more difficult. Consider for a second that pretty much everyone carries a device with photo and video recording capacity everywhere that could be used to make and share porn, that someone with basic art skills can draw it if you remove the camera from the equation somehow, and that if you include smut in all this that even just being literate is enough to make some. Ultimately, porn is a form of information, and in the modern age restricting information is very difficult, let alone trying to restrict information that literally anyone can independently create, from being seen by children who are naturally curious because they have been forbidden from seeing something but dont understand what or why.