Again, you are 100% correct. BUT again - he said he's passing them over for the INTERVIEW which, for all we know, that blue haired gal may just end up showing up with normal colored hair, piercings removed and end up being the perfect fit for the job! BUT, passing them over entirely for an interview, based on facebook is just plain bad management.
Interviews take time. And they can be emotionally draining (I personally HATE meeting someone and not hiring them, it kills me to get to know this person just well enough to say no). The whole pre-interview process is about saving that time and energy, gathering the data necessary to reject them before going through that. Also going through their FB page gives you an idea of how well they think things through. When I’m looking for a job step one is sanitize my public presence, make sure the voice mail message is boring, remove any odd signatures from my e-mail, hide the cool stuff on FB. Job hunting is a time to put on your Pro From Dover costume, and somebody who’s not thorough about that is probably not going to be thorough about stuff.