People tend to think of only 1st order effects. They don't tend to think in 2nd, 3rd, ..., nth order effects--not that it's easy to quantify the effects, but it's usually not difficult to see/imagine those potential relationships.

This is why a lot of rhetoric in general is so effective: it prays on focusing on simple first order effects instead of attempting to look at issues holistically. I'm not saying hollistic analysis is simple--far from it--but one needs to be aware that life is really complex with a awhole lot of gray areas.