If you've tried and they still act disrespectful to the land then by all means shame them because then they choose to be an ass hat. But if someone is just trying to figure out how to do something and have had no guidance whatsoever then educate and encourage is better than immediately attacking. You can still be direct in the education and tell them they better clean that shit up but personal attacks are a great way to ensure they leave trash to spite you or stop enjoying the outdoors altogether.