I mean, it might sound pretty manipulative of me, but I've found that the best approach to getting people to open up is to find something relatable, something that isn't out of place for anyone to say and that's a pretty bland statement. After that, you then follow it up with an additional comment that people are somewhat divided upon that's not too inflammatory, but you do it in a way that makes you seem almost naive or uninformed on the topic.
It's all to gauge their reaction and response. After they take the bait, you know everything you need and can proceed with a conversation or let it drop from there.
In my case, he seemed like a nice enough guy, so I used it to further probe. The most important thing in conversations like that is making concessions. People love to be told their right — even when they're wrong. But you can almost always find something in what they say that may hold some truth. You use that to feed their ego that way it doesn't end up in an argument, but rather, slowly making them consider what you're right about. People are pretty social creatures who want to find common ground. If done properly, you can find out a lot about people.
But that's just my experience. Maybe others have different methods that work just as well.