That is an appropriate forum for that behavior. The man came to a college event to speak and presumably take questions - am I correct? Are you suggesting the only questions allowed should be pro-creationist/ID? Now, a docent in a museum is not there to defend an entire belief system/theory/point of view. She's there to show people around the museum. Do you not see the difference?
I'm pretty sure that answering questions is part of the job description. And sometimes you get tough customers. They asked questions, she answered them, then she got a drink of water.
Are you saying you're unsure whether evolution is a belief system, a theory, or a point of view? Some folks don't mind the theory but think adopting it as a system of belief is quite another matter.