Hello everyone. I've seen Lindybeige mentioned before on this sub, but did not see any discussion about this specific video which makes some interesting claims, apparently citing primary sources.
Youtube link: https://www.youtube.com/watch?v=zViyZGmBhvs
The thrust of his argument is that a relatively small percentage of pre-modern soldiers (and actually including anecdotes from WWI and WWII) actually fired at enemy combatants with the intent to kill them.
He claims that in WWII, only ~2% of soldiers shot with intent to kill the enemy, when they were in a position to do so (so excluding soldiers that didn't see combat). That seems amazingly low. Should this video be taken with a grain of salt? I get that Lindybeige is not doing academic history here, but this is the sort of crazy sounding stuff that I would likely be spreading to friends and family; I'd like to know if there's a shred of truth to it.
This is not a direct, "real" answer to your question, but you might find this subs take on Dave Grossman's "On Killing" to be interesting as well as people's opinion of S.L.A. Marshall.
I think you are right to be skeptical of Lloyd. I enjoy his videos, but it's not just that he's not doing academic history, he tends to engage in a lot of speculation and "it just makes sense", even compared to similar YouTubers.
It sounds like his claim could be based on Grossman's book "On killing", which is itself heavily based on Marshal's earlier research.
The book is a very interesting read, save for the in my opinion shoe-horned in modern political discussion, but has been heavily critisized lately, especially as some of Marshal's research, upon which Grossman heavily relies, has been questioned.
Some earlier discussions on Grossman:
One.
Two.