Like StellarStory said, my reaction depends on the situation...
When I first began homeschooling, my grandmother was very... shall I say ...
concerned. She was completely anti-homeschool, and she made it out like this was a temporary deal. Every time her and my mother spoke on the phone, she would ask something a bit like this: "So, when will Morgan be going back to school?" And the first time I heard about this, I was shocked. Did she really, truly, believe that homeschooling was temporary? I confronted her (not directly) about it, and I found that she believed it was strictly a social issue and that homeschooling was just a way of me getting away from whatever was bothering me at school. I'd tried, and my mom tried, to get my grandmother to understand that this was permanent, that this was real, and that this had
nothing to do with any kind of social issue. It took a while to get her to understand, but finally after a year, she hasn't said anything about it. However, she still challenges that fact that we are getting an adequate education.
If the situation arises where someone is directly challenging whether or not I am getting a fit education, my first instinct is to say something like "I am in pursuit of knowledge, rather than knowledge being in pursuit of me." and quote some famous homeschooler, but instead I laugh it off and think "Are you serious?". I leave the talking up to my mother.
But, to the point, I do not tire of defending myself. I am feisty when people get in my way and challenge my beliefs. And yes, I would enjoy greatly, beyond a doubt, making a point to these kind of people in such a way that would
permanently turn their point of view around.