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/