When you demo somebody make sure to include yourself typing status in console to get their steam ID. Otherwise, you can get a demo of a greifer and post the steam ID of somebody else who didn't grief. If I was a dev, I wouldn't ban the steam ID you gave me.
Thanks stevo, I also have seen meatwad grief on several occasions. However, I couldn't remember at the time how to set up a demo, so I wasn't recording. However, I can also vouch that this guy griefs constantly whenever he is on.