[0] http://www.telegraph.co.uk/news/health/news/11981884/Cooking...
This is because poly- and mono-unsaturated fats had double bonds that oxidize rapidly. A free radical colliding with one of those double bonds will set off a chain reaction, resulting in rancidity.
In comparison, saturated fats have single bonds that do not oxidize as rapidly after a free radical challenge.
The processing step that the fake oils use will degrade the antioxidant capacity that you'd get from real, cold-pressed oil.
So, in summary:
PUFA's go rancid easily in absence of antioxidants.
Pure EVOO, though PUFA, has antioxidants that protect it.
If you buy "EVOO" in the US, it has possibly undergone processing (despite the label!), which means that it will have lower antioxidative capacity
Wiki article:
Seriously, though, to address why people find it hard to follow such rules one has to look beyond nutrition and medicine. People don't just eat to fuel their bodies, they eat to fuel their minds i.e. for comfort and pleasure.
This is why (I think) that small amounts of caffeine and alcohol are good: for a given level of mental stimulation they reduce the amount of food needed. Reducing side effects from any one source reduces overall damage to the body.
How does one reduce one's overall level of self-stimulation? For want of a better word this is a spiritual problem. Having an objectively valuable purpose or problem to occupy the mind with is crucial, but perhaps there will remain 'ups' and 'downs'. Look to traditional religious teachings or the AA for advice. Which advice, again, is going to be mingled with falsehoods and irrationalities. Intermittent fasting is becoming fashionable and may be part of the solution; it certainly bring personal issues into vivid focus.