Facebook links to wrong page

How are you getting “Sign in with Facebook”? Are you using a plugin or is your theme providing that?

That feature is not offered by default WordPress so something (plugin, or theme) is creating this without knowing what that is, we will have trouble helping you. Could you post a link to your site?

Disable all plugins on your site and activate each one until you see which one is adding the functionality. Once you find out, post in the forum of that plugin so the author can help you.