Even if you personally disable it on your own computer, anyone else connecting to your network (example: non-technical friend) will leak your password to all of _their_ facebook friends.
The only way to opt out of this "feature" is to change the name of your SSID to include _optout at the end -- or force EVERY SINGLE PERSON connecting to your network to disable the feature on their PC before connecting.
There is no other way to opt out.
https://www.windowsphone.com/en-gb/how-to/wp8/connectivity/use-wi-fi-sense-to-get-connected
https://www.windowsphone.com/en-gb/how-to/wp8/connectivity/how-do-i-opt-my-network-out-of-wi-fi-sense
https://www.windowsphone.com/en-gb/how-to/wp8/connectivity/wi-fi-sense-faq
http://www.howtogeek.com/219700/what-is-wi-fi-sense-and-why-does-it-want-your-facebook-account/
When connecting to a password protected router you are given an UNCHECKED BY DEFAULT option to share the password with your friends. What this means is, the user can deliberately share the password they know.
This is just as secure as any other system because once you give a user a password they could share it if they chose. Nothing here is "automatic" no data is being proliferated without user consent. If your employees leak your password this way, then it's the same as leaking passwords otherwise.
Again this not an opt-in-by-default scenario. It requires a user knowing a password to actively choose to share for each router independently.