I'm in a Melodic Death metal band myself. I can stand by your quote of saying that a band has a right to see what they want happening at their show. We fully support moshing as it's a sign that the fans are enjoying the music and having a good time. However, as an artist you're putting your art out there for the FANS. So if they do mosh and we didn't support it we're not going to tell them to stop. We'll leave that to the venue since it's not our job to babysit the crowd. Our only concern is putting on the best show possible. So if a band, in my opinion, does demand that a crowd knocks it off then they're turning their backs on the very people who are responsible for their success. Might as well pull an Axl Rose and just leave the stage mid-set while you're at it.