I have no problems with getting a warrant to search any phone. But the responsibilty is on the owner to comply, not the millions of other people owning an iPhone.
They want a back door. Period. Once they have that back door they will have a veil of secrecy under which to operate. We know how that works out.
I believe the search warrant issued by the court is just for this one phone.
If the Feds seek a warrant to search someone's house that doesn't automatically mean they want master keys to everyone's houses.