So when you are fretting over the weight of the Evil Granny Gas, do you also consider all the dirt, dust, dead bugs, dead birds, live birds, bird guano, bird nests, lost pens, wrenches, coffee mugs, nudie mags, water, etc. that your "large", twin-engine turboprop 19 seat airplane has acquired since it was last weighed?
So because we don't know the exact weight of the people on board, and the dirt, and the lost pens, etc., we should forget about using the exact weight of the fuel on board? I guess we could just come up with a standard fuel load based on distance along the route and forget about winds and other factors that affect the actual load of fuel required for a particular trip. Nice logic!
I could list a number of fallacies from here that would apply to your logic -
Common fallacies
They tend to weigh both carry on and checked in bags.
Yes, all carry-on baggage is weighed separately - it can be included in the standard weight for a passenger but we choose to weight them separately.
The only time an aircraft has too much fuel is when it is on fire.
That quote belongs in the same category as, "A good landing is one which you can walk away from. A "great" landing is one which lets you use the airplane another time." and "Your mom is so...." - they aren't correct and they get old fast.
Your quote might be correct if fuel didn't weigh anything. Unfortunately, it does. I can think of many cases where having less weight would be better - engine failure on takeoff, for one.