Joe, No repeater is ever safe open or closed. Scanners today can find PL tones on any frequency. So if someone wants to be an ass they’re gonna be. Even so, some radios are very easy to program and if someone really wants they can just key up every PL tone till they find the right one. Unfortunately there’s some nasty low life people that have nothing better to do but to cause interference on what ever tickles their fancy. Even on police, fire and rescue this happens. It’s those people who ruin it for everyone even scanner enthusiasts because a lot of jurisdictions are going digital and encrypted.