The title is a bit misleading. There’s nothing really new here yet; all that’s happened is that the U.S., as is totally routine, filed a reply to Apple’s brief, which was filed in opposition to the U.S.’s original motion.
Timeline: the U.S. government initially filed a “motion to compel” Apple to assist in procuring evidence. Apple filed a brief in opposition to that motion, and simultaneously released an open letter explaining why it opposes it. Now the U.S. government filed a reply brief, arguing in favor of its original motion and against Apple’s brief in opposition to the motion. That’s basically a non-story, unless the actual contents of the reply brief include anything particularly interesting or unexpected. It’s the way motions normally work: a party files a motion, the opposing party may file an opposition brief if it opposes the motion, and finally the original party may file a reply to the opposition brief. Once the issue is “fully briefed” (motion, opposition, reply), then the court holds a hearing and rules on it.
The call for a boycott is really off the wall. People are, I imagine, buying iPhones specifically because of apples stance. “Don’t buy this thing because it has a feature you want.” Unusual strategy for a boycott.