Continuing an unstable approach is not only negligent but constitues a violation with all possible consequences,
I agree that in an employee/employer relationship, a pilot must fly the plane the way the company procedures state, and doing otherwise is negligent - corporately. If company procedures say "on centreline and glidepath, configured for landing and flying at Vref +/- a set margin", then that's the standard. However, I'm not aware of a legal standard (in Canada, anyway) for a stabilized approach/touchdown. Yes, there could be a "negligent" approach and landing (probably a crash), but there's a wide grey zone between the on centerline, on glideslope on speed approach, and the assured to crash approach.
I can think of many examples where the only things stable during the approach are the rate of turn to final approach, the rate of descent and the rate of deceleration. I've done a number of landings, both to runway and to water, where topography precluded a straight in approach for more than short final. If you crossed the fence at the right speed, altitude, and lateral position, it was most likely not a negligent approach, and a decent landing is possible - though could still be botched too I suppose... On the other hand, I've flown beautiful, well set up approaches, to have Tower ask me to keep the speed up as long as possible. I had four times the runway length I needed for a landing, so it was not a problem to cross the threshold at"cruise" speed, and essentially, start my approach from there.
Negligence will be very hard to qualify for a landing, as what one pilot botches horribly, another pilot could probably make work quite neatly...