Unfortunately there is not a way to force safe Bing results. However there is a way Microsoft could if we shout loud enough. Microsoft could create a separate IP address for safe searches.
Googe has given an IP address (216.239.38.120) which resolves Safe Search results only! A network admin only has tp redirect Google.com (and other languages) to this address. This can be done with Tomato or DD-WRT router
firmware easily. The result is astonishing. It can not be circumvented, except perhaps by VPN or proxy.
For this reason, I have redirected quarries for Bing.com to 216.239.38.120.
If Bing would implement a similar solution, I could re-enable Bing results. Until then I have blocked it.
https://support.opendns.com/entries/57304954-How-to-Enforcing-Google-SafeSearch
Nevertheless, I strongly recommend OpenDNS to knock out a significant amount of Explicit Content. Advantages include network level filtering not requiring software on any device, protection for all devices, easy setup,
and a fast browsing experience. All you have to do is add two DNS addresses to your router
208.67.222.123 and 208.67.220.123