It's a very valid discussion and I think it must be linked to the fact that to an awful lot of people once you're pregnant your body's not your own anymore, it's like you become social property!
Think of all the prodding and poking that goes on by medical staff, not to mention the comments by just about everyone and complete strangers touching your tummy in the street! (It will happen.....)
I think the secret is not to be uptight about it. Relax and accept everyone will have things to say about your appearance during pregnancy, but noone says you have to listen.
Yes, your bodies going to change, but so did millions of womens' before you, and millions after. It's a small price to pay, lets chill out!
Water off a ducks back......