To answer my own question:
1) Man - **** no. I believe that it every mans' function to know some form of MA to protect the weak.
2) Olde man/woman - If it looks genuine, absolutely. That is just so wrong. Some people have no honour.
3) Child - This one is tricky. Some children have been corrupted to the point where they are far worse (and deceitful) than adults. If the child is really in danger, though, there could be nothing more awful than knowing that the innocent lifeless cadaver lying before me on the ground could have been spared from an untimely demise.
4) Handicapped individual - In many countries the handicapped people you see dragging themselves along the ground on little carts did something to deserve what they got. I feel no pity for them whatsoever, though again, if someone pushes a man in a wheelchair down a flight of stairs for giggles and ***** I can't stand by idly.
5) Young woman? These can be deceptive as well. If I was single: Absobloodylutely - every time.

Wouldn't you? But, as I am not, I would be cautious about this one.