Just to clarify the position of the ground staff.............
1. I doubt they were employed by the airline, they would almost certainly have been Handling Agents staff.
2. Assuming point 1 is correct, they would not make any decision of this sort without referring it to the airlines Station Manager because they have probably been hit with sanctimonious hindsightedness before.
3. If it happened abroad, or at a station where the airline went infrequently it is likely the Station Manager is a chasing agent and not a direct company employee. They also have limits to their decision making powers placed on them by the airlines.
4. The correct course of action would have been to discuss the situation with the crew, the airlines senior reps who have absolute say in this situation as stated by Cheeryguy, before presenting the passenger for boarding, and if time allows before checking them in but it is rare to have turnrounds of that length these days.
5. I am aware of incidents in the past where a handling agent has refused a passenger without referral to the crew only for the airline to tell the passenger 'if the handling agent had spoken with our crew they would have been accepted'. The Handling Agent was then expected to pick up the repatriation costs.
So next time you think that the ground staff are just fobbing the problem off onto you, please be aware that there might be good reason for their doing this................... not least how your airline has reacted in the past when they have.
I appreciate that the above shouldn't apply if it is the airlines own ground staff handling the flights, but then they have more authority.