> Instead I was treated as if I fundamentally had no understanding of algorithms whatsoever.

This and similar experiences, basically discovering the interviewer, potential boss, or worse, actual boss, is not a colleague but actually a shallow copy of what one would expect from someone in their role, is pretty common, especially (from what I've seen) in orgs with a clear divide between a "manager" class that is mostly composed of people with less experience than those they are managing, and those doing the work.

It's best, as you say, to just write off the time wasted on the discussion, move on, and be happy you don't have to work with them.