They enabled the perpetrator's planning and communications by supplying him the phone. I mean, they are just as culpable as Facebook, Google and Twitter...
...i.e. not at all, but a large and wealthy company to try and extort a settlement from.
By this logic you can sue the clothing company that provided them with clothes during their felony
I think the guy was wearing underwear at the time, so Hanes? can be sued too.
That's pretty much the point the GP was trying to make.
If they are sueing for allowing ISIS propaganda to be spread on Social Media, they might as well sue for not policing iMessage as well, I guess.