Your post is great. We participate in a very outgoing activity (skydiving) and people are pretty loose in their verbage and evenings at the bonfire get wild at times. Our daughter has been around it since an infant (17 now). We personally don't talk or act that way (as much) or do some of the evening hijinx you see. There are LOT of great and decent people, but there's all other kinds too - just like any other activity I suppose.
She's actually a much more clean/conservative kid than we could possibly deserve (she makes good and responsible personal decisions). I asked her once what she thought of a couple of the regulars that in our local camping crew after seeing them acting out and swearing, etc etc. She just looks me in the eyes and said, "Dad, I know who in our group are good role models and who are just bad examples. It's not a matter of age when people are playing." We've always tried to teach her to judge people by their actions only, not appearance, not their words, but their actions and character only.
of course, a couple years earlier, she had asked me why one guy was acting really stupid. I looked her in the eyes and said, "because he's a dumba**, sweetie". She was very thoughtful for a bit and then said, "ok, I understand". I'm proud - and absolutely terrified when she finally does break out of her shell - hopefully in college after out of the house....
You can't choose how other people act (except for being courteous to them while requesting they do the same to you). But you absolutely can affect your kid's maturity by walking the talk yourself.
I totally agree with you that the best way to teach/lead is by example. The problem is, if the children see something becoming more and more prevalent, it will be easy for them to think (especially at a younger age), "aaah, what does Dad know, all these others are doing it"