It does suprise me how far somebody can get into aviation without knowing some really basic things. Still, I suppose that if you have never had anything to do with maintenance, it's a fair thing to know nothing about engine shock loading etc.
I know of a case (saw the damage myself) where a self fly hire renter went off with the towbar attached, took a chunk out of the prop, chucked the towbar away, went for a flight, came back and said nothing.
The missing chunk was about 20x20mm - must have vibrated "noticeably".