Food is an issue of need from outside the body.

That was not the claim.  The claim was that saturated fats are not needed by the body.  This does not state internal or external sources, just requirement by the body.

 Antiarrhythmic effects of the Prostaglandin (PG) precursors arachidonic and Linoleic acid were demonstrated on three models of experimental arrhythmias, whereas the fatty acids linolenic and oleic acid proved to be ineffective in these models. In ouabain-induced arrhythmias infusions of arachidonic acid (1,0 mg/kg/min) caused a strong antiarrhythmic effect in 80 percent of the animals. 

Actually this is easily explained.  As they mentioned the AA is a prostaglandin precursor.  And as I have pointed out many times the most common cause of arrhythmias is a lack of blood flow to the heart leading to ectopic pacemakers that throw the rhythm off.  Prostaglandins though dilate the blood vessels and thus increase blood flow going to the heart and reducing ectopic pacemakers.

Although the real question was whether or not AA increased the rick of atherosclerosis, not arrhythmias.  Atherosclerosis is more likely to lead to death than most arrhythmias.  So getting back to the original claims does AA contribute to heart attack and strokes?  The answer is yes.  It is those same prostaglandins that contribute to arterial inflammation.  Arterial inflammation in turn leads to cholesterol deposition on the arterial walls over time increasing the risk of heart attack and stroke.

In addition the AA was used in what is suspected to be relatively healthy animals.  Long term exposure to the high levels of AA though again leads to arterial plaque build up from arterial inflammation.  As arterial plaque builds up though, blood flow to the heart actually decreases leading to an increased risk of arrhythmias.  So the study can actually be considered misleading since it fails to take in to account the long term adverse effects of AA.  That would be like doing a study on the effects of caffeine on the adrenals and starting out with healthy individuals.  But they only give small doses of caffeine for a few days and come to the conclusion that caffeine has no adverse effects on the adrenals.  Of course caffeine does adversely affect the adrenals, but this goes to show how easy it is to manipulate studies to show what a person wants to show.  Just like that study failed to take in to account the long term effects of AA on the arterial lining and arrhythmias.

 There are as many theories as research grant-giving bodies. AA as the causative factor is one of many, so is (was until recently) dietary cholesterol, microbial injury, excess iron, hyperinsulinemia, hyperthyroidism, genetics, saturated fat, transfats, polyunsaturated fat, chlamydia, stress, animal fat, plant oils, lack of fat, hyperglycemia, wheat (very recently), too much arterial exercize, too litle exercize, etc etc. Some of them explained some of the cases some of the time. Some better than the other. None of them explain all cases all of the time.

Nobody claimed that AA was the ONLY cause of cardiovascular disease from atherosclerosis.  If you check my older posts and you will see that I mentioned various causes including bacterial infection, xanthine oxidase, hypertension, diabetes, etc.  But all of these have one common denominator, which is arterial inflammation.  And what else causes arterial inflammation?  Arachidonic acid from animal fats.

 Even if that hypothesis were true then there is a question what is causing the immune system to become overactive? Are humans built such that some increase in the immune activity caused by some dietary change (i.e. more animal fat) were supposed to kill us by heart diesease where as a decrease were supposed to kill us by infections? I doubt! If they want to prove that atherosclerosis is caused by the immune system gone amok then they must find out what exactly does cause the immune system and the ensuing endotheliarl repair to go amok! Immune system is homeostatic - it stabilizes itself.

So when you want to know how sugar provides energy to the body do you also want to know each and every chemical process in the body that allows the sugar to be utilized by the body starting with digestion?  Or do you accept the fact that sugar provides energy to the cells?  Or do you want to debate that even further that it is really not the sugar but rather the ATP generated that is providing the energy to the cells involving numerous other reactions that must be verified before you accept it?

On top of that where is the evidence that there is even an overreaction by the immune system to begin with?  So I guess since you want to claim that the process involves an overactive immune system that is where your evidence needs to start.