I happen to be a commercial pilot myself and I obviously think this is indeed an embarrassing incident. Also remember I am not trying to defend this action, however;
as a captain, besides the responsibility of flying the plane safely and comfortable to your destination, you are also responsible for everything else that happens on the plane. If there is any irregularity on the plane before takeoff which can possibly become a problem during flight it is just better to not take off, wether it is a technical problem or something else. Therefore, if passengers were complaining, perhaps panicing (I wasnt there obviously), the purser would inform the pilot that the cabin is not ready for takeoff and has to taxi back to the gate, simple as that.
I know this is a boring story and all that, but the bottom line is that this is exactly what happened and the "irregularity" was removed, following procedures. Does not take away that this seems like a very sad case of discimination.
"When I hear music, I fear no danger. I am invulnerable. I see no foe. I am related to the earliest times, and to the latest." - Henry David Thoreau.