The problem with allowing something like the internet archive is that it lets you access a cached version of essentially any website, thus defeating the filter.

The problem with allowing something like the internet archive is that it lets you access a cached version of essentially any website, thus defeating the filter. Obviously a motivated kid will work that out and share it with their friends, and soon enough everyone will know about it. Same reason most adult/corporate filters block proxies. Perhaps if archive.org offered a "safe mode" of some kind that can be activated at a network level (as Google/Bing/YouTube and others do) then it would be possible for ISPs to allow access to archive while still limiting adult content. You can, of course, unblock your children's phone if you want, and install another filter or none at all. But I think as a default configuration it's not the worst thing in the world. Regarding the library thing, I've not been to one in decades but I'm guessing most libraries don't have porn, snuff films and ISIS recruitment videos... but sure there is collateral damage sometimes. In school, the overly aggressive filters would sometimes stop us researching anything to do with Nazis or biology.