Well said Raven. I also think it is perfectly acceptable to be immature at 18 because, well, you are immature at 18!

I think all you can do is offer advice when asked for it PZ, perhaps tempered with a caveat along the lines of "my parenting style/beliefs seem to be very different from what you believe but here is what i'd do....."

I also think there is a difference between giving advice about safety issues and parenting choices or theories. If someone told me outright my theories/beliefs/attitudes were wrong I'd be inclined to tell them to get knotted and think they were being a judgmental biatch. Especially if I was 18. It's partly in the delivery of the message and partly in the content (ie. Which "wrongs" you seek to right) that makes the difference.