Sciolistes,
I don't think anyone here has suggested you attempt landing overweight if you can't meet landing distance and missed approach requirements.
Sure - the margins will not be the same as if you landed at the same airport at MLM - but we operate our aircraft near the requirements often - taking off a couple of ton under RTOM or landing close to RLM. No pilots woth their salt would refuse operating close to the limit as long as you are positively on the safe side - the same principle should apply during a medical emergency.
Other than that, I agree with what I percieve your sentiment to be - namely that we should never consider endangering the aircraft or its occupants just because some poor soul has keeled over in the cabin.