In other words, we believe that the modem should be seen as a black box and should be threated as one by hw designers, sw developers and users. Trusting a black box without any control is insane regardless of upgrade possibilities (the firmware may contain malware right from the very beginning, how would you know?), and with such control any bad sides of possibility to upgrade don't matter anymore.

Anyway, while I understand and fully respect Richard Stallman and his concerns, IMHO it's better to provide the freedom to upgrade the firmware to the user. It gives some small hope for some free replacement in the future, even if it's insanely hard to do due to deep "tivoisation" of practically any modem available these days (not that it would be possible to use it under most of legal regulations anyway but one still can come up with some legitimate and legal lab usecases). If every phone would work that way we wouldn't have now projects like OsmocomBB, which works for instance on upgradable GSM module of Openmoko Neo Freerunner.

(for a long time there was only non-free flasher available for Calypso, but recently some REd one popped up, so it's now possible to reflash Freerunner modem with free firmware using free flasher. It wouldn't be possible at all if Freerunner would comply to FSF rules since its release)