i had some problems with the Facebook login on my development machine (Jive 18.104.22.168). There were "Connection refused" errors while requesting the Facebook API. I was able to track it down to the class:
In the method loadRegistrationData() a default (self-instanciated) HttpClient is used to request data from Facebook. I think this instance should be build by the factory method provided in the HttpClientManager as this is provisioned with all the settings incl. the HTTP Proxy that can be configured in the admin console.
One can use the Facebook-Login in (on-prem) environments where a proxy is needed for communicating, but then no credentials will be transfered from Facebook which makes this login method not that valuable.