You know, it's funny. People hear pregnancy, and then they think they have a right to be involved in all sorts of ways, that they actually don't. They call you fat, "wow, are you getting fat in the face!", (if it's rude to say to a non-pregnant person, it's still rude when you are expecting), they judge what you are having, "You should have a boy, don't have a girl", (as if that's even up to you, kinda already determined), and they even judge your method of birth, "oh, you HAVE to do it like this, because I know so-and-so, and she had this sort of experience, and you will, too", (which of course is ridiculous).
The only solution is to just not talk to people about your birthing options, or any other options you don't want negative opinions on, (hello, baby names anyone?), because it's like they just can't help themselves but put things down that THEY don't like or don't understand. But it's not up to them.
My mom told me she was upset that should couldn't be in the room with me when I gave birth (she lives in another state) and I replied, "well, you didn't even ASK me what *I* want, and I just want my DH there, which he will be, so no need to be upset."
In the end, you are doing more research than them, and it's more current then who knows what they are telling you. If you need something to show them, check out the ACOG's site, and they show guidelines and recommendations for OBGYN's on all sorts of things, including VBAC. And yes, they recommend VBAC, and even trying for a VBAC after 2 c-sections (which I am hoping for), which was just changed in 2010. So most people don't even know about that. But in the end, it's safer and puts a women at LESS risk, to VBAC. So you know you are doing the right thing for yourself. You don't have to prove it to them, but show them the ACOG's site, if they need something to check out. It's hard to dispute that.