(Note: This post has been updated (1) as of 11:49 AM Eastern on 18 Feb. See below.)
In respect of my provisional agreement with Alex Ross in an update to this post, and my in-large agreement with Marcus Maroney by comment in the comments section of this post, I suppose I should clarify my position regarding booing by an ideal audience (i.e., an audience made up entirely of the musically informed and knowledgeable) at the classical music concert.
My position on this matter is perfectly straightforward: booing should be as rare a thing as a standing ovation. One does not boo a performance merely because it was substandard. Response to that should be by appropriately reduced applause, or none at all. One ought to boo a performance only in those rare cases where the performer(s) showed himself (themselves) to be clearly incompetent to undertake the performance in the first place; was (were) clearly insufficiently prepared for the performance; or and worst of all manifested in part or in whole a clear indifference to the music no matter how competently performed.
Just for the record, in more than a half-century of concert-going, I've never encountered even so much as a single instance where booing would have been the appropriate response.
Opera is another story.
Update (11:49 AM Eastern on 18 Feb): Lisa Hirsch of Iron Tongue Of Midnight comments:
Note that ACD is talking about something that is difficult or impossible to find - the ideal audience, "made up entirely of the musically informed and knowledgeable." Where might one find that audience? And what is one to do in the less-than-ideal real world?
Answer: One can't find such an audience today, generally speaking; ergo, the value of our present classical music concert "rules of conduct"; an idea made clear in the update to a previous post above linked.