I'd infinitely rather push on a fixed pitch propeller near the blade root than on the leading edge of a low wing. Common sense should indicate that a fixed pitch prop structure is not going to be overstressed (in operation props are radially stressed to ~20,000 psi), and the supporting crankshaft etc is certainly able to withstand the moment of reasonable hand force.

Maybe there is actually a reason for variable pitch props, but it also seems hard to believe. Does anybody know why?