Jim Logajan writes:

I'm sure the FAA would have been equally diligent to complaints of unsafe
airplanes towing banners saying something like "Eat at Joe's".

A bad seat belt can lead a banner-towing aircraft to tragedy, just as surely
as a politically-incorrect message. It's not like a failure to maintain a
fleet of 737s, or ignoring ADs for a couple of 747s, or trivial stuff like
that. This is a question of seat-belt conformance, which has the absolute
highest priority with the FAA because of the fearsome danger it represents to
aviation safety.