Why is it important what do the survivors of the attack think? Justice system is supposed to be objective - we don't ask a widow what should we do with a murderer.
If the families say, actually, we'd rather you didn't do this, then that makes that particular argument less effective.
The FBI's proposed interpretation of the AWA's powers is going to be a tough sell to appellate courts, as far as I can see. Their main play here has been to try to generate enough of a PR shitstorm that Apple decides not to challenge the writ and just plays along. And if that doesn't work, they're hoping to provoke enough outrage when Apple wins that congress is nudged into giving them the powers they want.
Insofar as there is a political/PR battle, I think its just as likely that they want to lose publicly and use that to reinforce moves under way for getting specific new authority legislated. It's perhaps not coincidental that the various All-Writs Acts cases all came up after discussion of Congress adopting rules regulating provision of consumer end-to-end encryption.
To be clear, I'm assuming when you say 'lose' you mean the case, not lose the PR battle. The latter is of course always a bad idea when you want to get your way.
Ya, we do.
On the other hand, since in reality the rule of law is often way weaker than the rule of, say, public opinion, or bribes, etc. etc., it of course matters a lot what the victim thinks; if one thinks that the whole purpose of the FBI is to sway the public opinion to gain power, then of course the way to counter this is to sway the public opinion in the opposite direction, and the public will care about the victim's opinion. (In general, it feels that the share of the population truly believing in "the rule of law" as in "let's follow these written rules literally instead of arbitrarily interpreting them to suit our current desires and then priding ourselves on having and following great laws" is rather small; I'm not sure if it's good or bad...)
Opinion also sways what gets prosecuted. This cuts both ways in that the prosecutor wants to appear tough on law or favors can be had because of "affluenza" etc. Neither is right and I do believe good laws need to be applied consistently.
So yes, there are bounds where you have to ask the victim. Often you don't even have case when victim decides to settle (not in cases of murder obviously).
So, they get longer sentence and less help. What are they going to do when they're out there in the street?