In 2009 it approved AT&T's acquisition of Centennial Communications. So clearly the FCC approves plenty of mergers.
Maybe the FCC staff harbors a bias against AT&T itself. Again, the agency approved AT&T's Centennial deal.
Or maybe, just maybe, the FCC -- along with the Justice Department -- is doing its job by studying a potential merger's antitrust implications and concluding, based on its analysis (and not AT&T's lobbying and PR campaign), that consumers would be poorly served by the elimination of a major wireless carrier.
I side with the FCC on this, but since I'm not an AT&T attorney, I can't possibly be fair-minded or objective.