Given the venue, it's not much of a leap. Like asking how you know a shopkeeper in Palermo is Italian. He might not be, but probably is.
That said, I've spent time in Berkley and have had discussions with business owners. They were nominally liberal to a person, but when it came to their own money and business they magically turned into free-market private property enthusiasts.
Not surprising. I've found that a liberal can be accurately defined as somebody who is generous with other people's money