Part 91 requires you to operate in accordance with the flight manual limitations.
Below is a typical AFM from a Part 25 a/c.
2. MAXIMUM ALLOWABLE TAKE-OFF WEIGHT
The maximum allowable take-off weight is limited by the most restrictive of the following:
• Maximum approved take-off weight
(Refer to Chapter 2; LIMITATIONS – STRUCTURAL WEIGHT),
• Runway length available,
• Climb requirements,
• Obstacle clearance requirements,
(First, verify if the second segment of the take−off flight path extends beyond a pressure
height of 1,500 feet above the airport and consider if potential adjustments are to be made.)
• Maximum demonstrated brake energy,
• Maximum tire speed,
• Wheel brake cooling limitations
(Refer to PERFORMANCE – TURN-AROUND TIME – Cooling of Wheels, Brakes and Tires,
in this chapter).
Note that obstacles are in there as well.
It seems pretty unequivocal to me - which bit of Maximum Allowable Takeoff Weight do people have a problem with?
Apart from the legal considerations, why would anyone not want to take the climb performance into account? A 2.4% gradient with no obstacles or 35 feet clearance if there is seems pretty sphincter tightening to me
Added to which, in my book I'm being paid to keep the boss safe - and he thinks so too. He would probably be mightily unimpressed (= me fired) if he though I was gambling with his and his family's safety.