Oh, my friends, I have done it! Not quite eight months into child two, I have discovered the perfect, never fails, one size fits all response to all the DIRE WARNINGS and ASSHOLE OBSERVATIONS to which parents are constantly subjected by the general public. Like, "That baby doesn't have a HAT!" and "She's still using a BOTTLE?" Like "You know, if you let that baby sleep with you, he is going to WANT TO SLEEP WITH YOU FOREVER" and "If you feed that baby whenever he's hungry, he's going to expect to just EAT WHENEVER HE'S HUNGRY." Like "Oh, I've heard that babies who don't crawl don't ever learn to read" or "Shouldn't she be walking/talking/self-feeding/conjugating Latin verbs/calculating Pi by now?"
It's true, I have formulated the perfect response. That response is:
It helps if you put on a bit of a bitch face while you say it. Most people shut right up, but some are persistent and start to explain in detail exactly how you have strayed from Ideal Parenting Practices, in which case, just do it again as often as needed. "And? And? And?"
Works like a charm.