This is a great example of Internet censorship run amok. There is nothing unsafe about unrestricted wifi, and no it doesn't "attract pedophiles and sex offenders".
For bad people, there's Tor, VPN, anonymous sites, and CloudFlare. Like many such things, you aren't stopping the bad guys determined to get around the limitation. Instead, what you end up blocking are those who aren't bad who get caught up in the grey area.
I've been blocked from accessing my own blog because of censorship filters at public WiFi hotspots (specifically, Panera). My blog is vaguely hacking related, and therefore blocked for "illegal" activity.
