So, if I understand the OP correctly...
1. The teacher was not prepared for the question.
2. The teacher feels she handled it badly.
3. The teacher has decided that she will refuse to answer the question, if it comes up again in the future.
That seems quite unfortunate. I would rather the teacher had prepared a concise factual answer for any future questions, rather than hiding her head in the sand.
But regardless, the fact remains that teachers are human and they make mistakes. Your children should know that not *everything* their teacher tells them will be true. They need to learn to evaluate what they hear.
Case in point... When my children were in kindergarten, the French teacher once told the entire class that, "Down is the fur baby birds have before they grow feathers."
Since the class was studying "what is a mammal, what is a bird" in class, I alerted the homeroom teacher that there might be a problem here.
When the French teacher left, the homeroom teacher asked her class, "Do baby birds have fur?"
Despite the fact that the class had been told many, many times over the past week that "mammals have fur or hair, birds have feathers", almost the whole class stuck their hands in the air and said, "Yes! Down the fur baby birds have before they get feathers!"
The rest of the class just looked confused.
The homeroom teacher spent the rest of the afternoon trying to convince her class that down is not fur, and birds only have feathers. Some of them flatly refused to believe her.
BTW - I'm a big supporter of homeschooling, whether or not your children actually attend school outside the home. I've homeschooled part time and full time, but there's never been a time when I haven't been teaching my kids.