The flight crew would have had a maximum take off weight for the conditions that takes into account all the margins required to safely operate the aircraft. 1kg under that weight they will go. 1kg over, they don't. As simple as that.
I suspect the issue is that EJ simply operate too close to that figure. This is why you don't get whip rounds on other airlines. Exactly the same as the issue I had last year with them. Pilots didn't have enough flying hours left to make the 1 1/2 hour flight I was on. No backup crew available. Flight cancelled.
Here's a thought, though. Do you think it was just the passengers' baggage in the hold or a load of mail and other freight they were being paid to carry too? Wouldn't you expect the passengers to take priority?
Personally, I'd have asked them to take off the trolleys of food, perfume, duty free and all the other cr@p they were hoping to sell me on the flight. 
Absolutely correct KW ... and to elaborate on your question .. passengers are not "weighed" as we all know .. an average weight is assumed (used to be 185 lbs male 155 lbs female in my day ... no idea what it is in kilos or if its changed).
All cargo and baggage is weighed, fuel weight is ALWAYS known, as is APS (Aircraft Prepared for Service - oils/water/galley supplies etc etc) weight.
The max takeoff weight (MTOW) does vary however, given conditions. In the ice/snow/ poor visibility of recent days the MTOW will be reduced for performance reasons - usually the ability (or lack of it) to stop in the event of an aborted (abandoned) take-off.
The easiest way to reduce weight is throw passengers off .. no reweighing of anything .. you want to lose 600 lbs .. 4 men plus bags ..OFF .. dead simple. ... any other method is time consuming and protracted ... and will lose you your takeoff "slot"... which means many hours delay and cost.
So EJ simply took the easiest and cheapest way IMHO .. as they always will...
