I would probably say something similar to what Christy mentioned. If you don't want to/aren't ready to engage (which is perfectly fine... this stuff I can be hard to wrap your arms around), focusing your response on the neutral needs of the group is perfectly reasonable.
Going a step further, when I find myself in that position, I will often turn the conversation because, as I see it, I am not on the defensive position. They can believe what they like, but if they want to discuss it with me, I am clear up front that I can share information, and am happy to. If they want to learn with me, fine. If they have another agenda, then there are many other conversations we can have:-)
Depending on how close you are to this person, you can certainly not respond at all. If you are later asked about it, an "Oh yes, I did get that. Thanks for the info." You don't necessarily need to explain yourself.
The homeschool world is full of truly special brothers and sisters in Christ who bring much light to my life, but flexibility usually isn't a hallmark trait of the group as a whole, lol. Good luck.