If the commander makes the decision to fly slightly overweight, he or she has descied to either misrepresent the true configuation of the aircraft on a weight and balalnce document, or to produce a true representation of the configuation, which would later be the evindence that the authorities would use to find fault, and the insurance company would use to deny a claim.
Such a decision is the same as deciding to fly with a known defect in the aircraft. You are deciding on behalf of the crew, the passengers, and aircraft owner, and the insurance company. They are all entitled to have their opinions considered. You might be willing to say in advance to each party that you are going to deliberately fly with a nav light U/S on a day only flight, but I bet you would think twice before you told each that you were going to fly the aircraft overweight!
If you need to carry members of our heavier society, either carry fewer of them, or choose a bigger plane. Also consider that nearly all aircraft design is predicated on 170 pounds per seat. That is not only for weight and balance planning, but the seat and floor strucure, and seatbelt attachements. We all know that there is reserve strength built into aircraft, but when I see a really large person in a seat wich I know was designed for a 170 pound person, I have concerns. When I see three or four large people in an airliner row, I get even more concerned.
A Cessna Caravan crash in Canada a few years back had as its root cause, the decision the pilot made to carry a person in each seat, and then embark into icing conditions. It might have worked, other than each of the persons was reported as being heavier than the standard 170 pounds, some apparently, by quite a lot. The plane was quite overweight, and the pilot decided to fly it. He de not make that decision again.
A decision to fly within the limitations is the only decision you are entitled to make, unless you are on a design flight test.