Don't feel like you need to be the one to explain it all to everyone. I'm really comfy with public speaking, but I still wouldn't want to give a spiel on Primal vs. CW nutrition without doing some specific preparation. So have a few resources in mind, and mention those by name to anyone who is interested. This website is an obvious choice.
I'm giving a few people copies of Taubes' book Good Calories, Bad Calories for Christmas. It does a pretty darn good job of toppling the food pyramid. So my response to criticism would be "Let's talk more after you've read the book I got you." LOL, I'm evil like that.