Make it a habit to *always* check the mixture and magneto switches before going anywhere near the prop.
Mixture, Master, Mags.
As after every flight.
I think we can't compare the force on a propeller during operation to being pulled by hand. The prop is twisted to produce equal (as far as possible) thrust from root to tip. If you pull on the tip you bend it because you only apply force on this particular point. But I don't know if it is actually possible to bend a blade by hand. I think I just have to live with it that airplanes are being pushed around like this... I can't always be there to correct everybody...
