That is a really clever mixup of different argumentation modes. That being said, Mr. Cochran strangling one of his opponents would still be only weak evidence that it is not so difficult for humans to psych themselves up to kill another human.

First of all, he hasn't actually done it (I presume).

Secondly, we know it's difficult, not impossible.

Thirdly, we know there are sociopaths and psychopaths who can do this without much thought, as well as perhaps normal people who have become desensitized to killing. Fortunately these are a small percentage of the populace.

There is, in fact, a large amount of research that has gone into studying the minds of people who kill: in wartime, in criminal activity, in law enforcement, and so forth; and there is a strong consensus that for most people intentional killing is hard. For example,

In World War Two, it is a fact that only 15-20 percent of the soldiers fired at the enemy. That is one in five soldiers actually shooting at a Nazi when he sees one. While this rate may have increased in desperate situations, in most combat situations soldiers were reluctant to kill each other. The Civil War was not dramatically different or any previous wars.

In WW2 only one percent of the pilots accounted for thirty to forty percent of enemy fighters shot down in the air. Some pilots didn't shoot down a single enemy plane.

In Korea, the rate of soldiers unwilling to fire on the enemy decreased and fifty five percent of the soldiers fired at the enemy. In Vietnam, this rate increased to about ninety five percent but this doesn't mean they were trying to hit the target. In fact it usually took around fifty-two thousand bullets to score one kill in regular infantry units! It may be interesting to not that when Special Forces kills are recorded and monitored this often includes kills scored by calling in artillery or close air support. In this way SF type units could score very high kill ratios like fifty to a hundred for every SF trooper killed. This is not to say these elite troops didn't score a large number of bullet type kills. It is interesting to note that most kills in war are from artillery or other mass destruction type weapons.

If one studies history and is able to cut through the hype, one will find that man is often unwilling to kill his fellow man and the fighter finds it very traumatic when he has to do so. On the battlefield the stress of being killed and injured is not always the main fear.

-- William S. Frisbee, The Psychology of Killing

If you want a more detailed look at this, including lots of references to the original Defense Department research, there are a number of good books by army officers including On Killing by Lieutenant Colonel Dave Grossman. One of the originals is Men Against Fire by World War I Officer S. L. A Marshall. Bruce Siddle's work, more focused on law enforcement, is also worth a look. E.g. Sharpening the Warrior's Edge.

None of these are perfect or irrefutable evidence. For instance, the research I'm aware focuses primarily on U.S. and British troops and police officers. It's certainly possible that this is culturally conditioned and the results might be different elsewhere. However, I've yet to see any strong critiques of the general consensus about the difficulty of killing in war. The best evidence we have is that killing is in fact difficult for most people, most of the time, even in war.