I'm not trying to convict anyone - in another comment I note that these situations are often unclear, and many very well-intentioned people may not even realize they are harming or undermining someone (and they probably think highly of that person, too!). To be honest, my primary impetus was to explain why a comment like this is actually sexist (there seemed to be some disagreement on that part) and why it is harmful. It's not always intuitive, since we often describe our friends as "attractive" or "sexy" without a second thought in a friendly/social context.
I'm not trying to say that the introducer was sexist - the behavior was.
Edit: From the downvotes, it seems that there is disagreement here - which part do people take issue with?