The primary source of which I am aware for comments such as those you refer to is Massad Ayoob. He has made those statements in print several times. Since he spends a fair amount of his time serving as an expert witness at trial, I'm going to suggest that he's a well-qualified expert witness on the subject. And even if he is wrong, and only once in a blue moon is it an issue, why in the name of common sense do YOU want to be the guy with his tail in the crack?
I'm sure that you could ask Mr. Ayoob by sending a letter to any of the magazines he commonly writes for, or through LFI in New Hampshire. Ask where he gets these ideas.
My take on it is this:
He might well be wrong, but he COULD be right. If he IS right, surely there are hundreds of guns available and hundreds of loads available to do the job without opening you up to this kind of emotional manipulation of the jury.
So give it some thought, pick a nice All-American, patriotic, sincere gun, loaded with a powerful factory load with an innocuous name, and hope that when you are second-guessed at trial by 12 people that know NOTHING about guns, or self-defense, that you haven't done something stupid to make them less sympathetic. It's cheap insurance, and if he's wrong, it has cost you very little.