What I don't understand here is why some of the people commenting here (clearly the ones who fly way up there) are trying to justify policing 121.5, because that is what you are doing with all this rubish about a CPL/ATPL whatever knows about VFR but your average PPL has no idea about what they do. Is there some sort of urge to become the worlds greatest
when you sit in front of those glass instruments? As far as I am concerned anyone who deliberately interferes with another aircrafts transmission (whatever it may be) should be prosecuted, as some commercial pilots here have tried to justify it with 'we don't always hear the whole transmission' shouldn't that just secure the fact you shouldn't be transmitting at all. As DX has said it's only a matter of time before you step on an emergency and this time Guard never get the message.
Let the ATCO do his/her job.