You and parent are both thinking that it is Facebook's fault that third-party service providers are offering FB login.
Is it FB's fault that your favorite website is only accepting user comments unless you login with a FB account? No!
FB has done its good part. I am not here to argue with you or anyone about whether FB is respecting users' privacy and security demand. But now FB gives developers a new login option so that a site can allow users to do something like leaving a blog comment without revealing personal information such as name to the website. FB has done its good part as a platform.
If your website only offers facebook as the only option, that is not FB's fault. Should a website offer more login options? Why are services related to programming and source code usually come with a twitter or github login option instead of facebook? Because nowadays programmers tend to have a Github (or Bitbucket) account.
So why so much negativity around this new feature?