Stay off guard! There's no justifiable reason to clogging it up with nonsense. To the gentleman saying that if any relevant conversation comes up on 121.5 everybody would shut up, how do you expect it to come up in the first place if some rubbish is being xmitted at the same time?
Please, stay off guard. As already said, it is the last line of defense when things are not going the way they usually do. Go talk to an FA or something if you can't keep yourself entertained in the cockpit