Daly and Boyer might also believe that Stephen Belichick is being groomed to eventually take the DC role, or at least that he'll be given every opportunity to win the job.
I don't see BB promoting his son unless he thought he could handle the job. At the same time, he has kind of gone out of his way to try to bring Stephen along, making him the safeties coach, a responsibility that involved working with some smart veteran players with whom he already had relationships from Rutgers (McCourty and Harmon), and now bringing in Schiano to be DC, with whom Stephen also already had a strong relationship. He's certainly doing everything possible to put Stephen into a position to thrive and grow within the organization.
BB is all about winning and rewarding people for performance but things get complicated with family and its pretty clear that the whole football family thing, from his father's mentoring of him and now his mentoring of his sons, is really important to Belichick. I don't think it would be crazy for Boyer or Daly to look at this whole situation and wonder if they would get a truly fair shake.