Some useful info here on discounting inflated porn-viewing stats.
It may be possible to get a more accurate number, but I'm not sure if that would show pages loaded successfully or still include a number of frustrated attempts.
It may be that we're talking about a problem centered on a handful of hardcores who keep trying to load porn, possibly on multiple tabs at once, despite getting through only occasionally due to bandwidth shaping.
That seems like a manageable problem under some version of the current procedures. Stiffer penalties might be part of the solution.
If we want to remove any chance of anyone ever loading inappropriate content on a library computer, that will mean blocking email and Facebook, or disconnecting computers from the net altogether.
Short of advocating for those solutions, we're all negotiating the best compromise in a clash between legitimate principles of access to information and a safe, welcoming library environment.