I would agree that some of the things you are describing are not appropriate. However life does seem very different when comparing children with younger siblings and those with older. I wouldn't have dreamt of letting my eldest child watch Borat at the age of 10, but did let my younger children. The younger ones with older siblings are so much more "grown up" in many ways and although still vetting what they do, you have to let them get involved in what the older ones are talking about.
Having said that if we have their friends round and are watching a DVD, I would always check with the parents first if they were happy to watch something aimed at an older age group.
I have also drilled into my kids that there will always be things that they pick up from the older kids at school, but they need to make the distinction between what is acceptable within their peer group and within their family. They have become pretty good at this. I don't think you can hide your kids from what is going on around them, fortunately the oldest of siblings will retain some innocence for longer.
There are a few absolute no-nos in our house, mainly because I am too embarrassed to watch them with the kids