Please, please remove it. I actively avoid sites with fb logins, as it appears others in this thread do as well. Your idea can stand on its own without that sort of crutch.
I get that you might like it, that's fine, but it's not serving any good purpose here. Google login would be more widespread if you must have a 3rd party button. Yes, Google track as well and yes, that's also going to put people off, but if you feel the need to have one at all, get a more useful one. Or better yet, remove them all, have local user registration and put a hook in place for developers to plugin other buttons using different contrib repos. Then you can have both without polluting the core project with 3rd party deps.