Similar issue: I worked with someone via email for several months thinking they were female because their name is Kim before a coworker mentioned "uh, pretty sure Kim's a dude." You run into similar issues with e.g., women named Chris. I don't think being thrown by situations like that makes anyone look like an idiot.
Looking at it from an ethnic perspective, I'd be similarly thrown by finding out a guy named Santosh was a European white male.
Ideal world, sure, we wouldn't make assumptions about identity based on names. But it happens. I'm not sure that there is an answer that'd make everyone happy, to be honest.