I think that the comments come from an incredible amount of insecurity, and an unwillingness to be introspective.
I dealt with this too--and frankly, it was the single hardest part of my pregnancy the first time. It started in the OB's office: "Oh, lots of women *try* to have a natural childbirth. But I want you to know that only about 10% of them do it, and that's why we have pain relief measures and a whole staff of people here to help you get through this."
And then after the baby's home: "Oh, you'll use that swing so much when the colic kicks in. No pacifier? But he'll suck his thumb! Yeah, I thought I was gonna breastfeed for a year too. But the cracked nipples, the bleeding,.."
And when baby is around 9 months: "You have to start disciplining him. Why do you let him crawl wherever he wants--you need a playpen. When are you going to buy a crib--he can't stay in the bed with you much longer. He's manipulating you, you know..."
And so on. It drives me nuts too. One very effective way to deal with it, for me, is to simply ask, "Why?"
When someone tells me the baby is "manipulating" me, I'll ask, "Why do you think so?"
"It's obvious!" they say.
"Not to me. Why/how is he manipulating me?"
They can't back up their beliefs with a logical, concrete explanation. Have you ever asked these parents WHY they believe what they believe? How their parenting relates to those beliefs? What their ideal "end product" (kid) is? What kind of PERSON they want to raise?
DH often says he wants to raise our sons to be men he'll look up to when he's old. That's OUR goal.
When I had ds2 (who is 11 mo) I heard a lot of the "when you have two, you'll see how..." and what I found--gasp--was that I parent ds2 in a MORE AP fashion than I ever did ds1! And because I stuck to my guns with sd1, a lot of the "issues" (no pacifier, no crib, etc...) couldn't be thrown at me as being "idealistic" because I could just say "hey, it worked for Ben." That shut them up.
So I don't have any advice overall. Just ask why.