Before we get too judgemental, I was operating out of Pisa a few years ago on a holiday charter - B737-300 with an inop APU with a surface temp of 32 degrees.....as soon as the doors were closed, the CSD reported that the pax were very uncomfortable and the cabin temp indicator showed a cabin temp of 40 degrees. I asked GND if we could start an engine for air conditioning and they said no. I called the pushback co-ordinator and asked him for ground air conditioning as a priority which had been unavailable (of course) and was told to stand by, and I asked the CSD to open all main doors for ventilation, to which he reported that he couldn't because there were no steps in place.
The CSD then told me that the pax were panicking due to the high cabin temp and with no aircon and I couldn't see any options left apart from a rapid disembarkation. The FO called ATC again to try to explain that we needed the engine started for air conditioning only, but they clearly had the B team on and again told us that we had to wait for start clearance from MILAN CENTRE. At this point I was on the verge of declaring an emergency in order to get someone to recognise that we had a problem, the cabin temperature was soaring and no-one outside was remotely interested when all of a sudden Pisa Ground gave us start up clearance. To this day, I have no idea what I would have done if I hadn't been able to get the air conditioning on line.