A chick hatching from an egg. The chicken or the egg causality dilemma is commonly stated as which came first: the chicken or the egg?. The dilemma stems from the observation that all chickens hatch from eggs and all chicken eggs are laid by chickens.
Unpolarized light can also become polarized when it is scattered in air (also known as Rayleigh scattering). This occurs due to the fact that the EM waves cause the electron in air to vibrate, producing radiation and causing polarization of the light.
Ian, that site does not support your statement. It only says that the Wolf Effect occurs at the source and so doesn't require a scattering medium for the redshift to occur in transit. The Wolf Effect does require scattering of light at the source whether you want to admit it or not. It is basic physics.