You seem to be assuming that the company's goal is to find a reason to reject someone. That's not correct.
If anything, it's tilted in favor of candidates that have the same hobbies as interviewers.
Look, I know it sounds confrontational, and I don't go into interviews expecting a hostile environment. But I also don't go into interviews expecting to speak of anything other than things directly related to the business.
I would be very uncomfortable if asked to speak about anything not directly related to the business or business environment there.
It is illegal for a company to not hire on undue reasons such as race, religion, political affiliations, etc., but you are entering into an employment relationship, and it is not unfair to understand more about the person you are paying to work with.
(After all, I think that leaving work at 6:30PM to go to a Haskell Users' Meetup at 7:00PM where you will drink sugary, caffeinated soda and/or beer, eat bad pizza from a corporate chain, and watch an hour-and-a-half presentation on a programming and theorem-proving suite that is perpetually unready for use on machines with less than 8GB of RAM is downright insanely messianic language fanboyism. That doesn't mean I didn't go right along and watch the presentation to be sociable about it and to give everyone their time to make their case. Hell, it doesn't mean I didn't have a good time, even if I left after my coworker's presentation because I didn't want to stay until 10:00PM to watch a theorem-proving presentation I couldn't understand.)