Earlier quoted context omitted.
Simple: it is Apples problem if their servers aren't secure. You don't owe apple free work. Delayed disclosure is a nicety, not something you are obligated to do.
So there is no ethical responsibility to protect the users who will be left vulnerable to this exploit? Remember the danger here is screwing people who have iCloud accounts. It's not like Julie the housewife in Minnesota, had any say in the security of Apple's products.
By going loud and public, you ensure that the company has to do something to save face. It can't just be forgotten on some manager's desk.
And the fact is, you, as part of the public, would only know about the times when somebody goes loud about an exploit. For all you know, there might have been hundreds upon hundreds of times when security researches have gone to the company and been outright ignored, and when one finally goes loud with what he has found, you say "He really should have done this more quietly, it would have been much more responsible"