A large fraction of people will shoot if someone they deem an authority figure says they have to and gives them a good reason to justify it.

Reference please?

This is an instance in which the call for references is ridiculous enough that I think this is a sufficient response:

gestures broadly at the entire history section of the library

I'm assuming they are referencing the somewhat contentious Milgram Experiment.

Stanford prisoner experiment is also applicable

Can you lay out the conditions under which you'll accept references? I've had a lot of issues before where I provide this sort of evidence and the counterparty relentlessly and tediously explains why every single source is either wrong or doesn't meet their arbitrary standards, so I want to be sure this won't be turned into one of those situations.

I'm genuinely interested in how that perspective came to be since it is, to my world view, a shocking and hard to believe claim. But, my surprise isn't worth anything. I'm unable to find search term that gives something relevant, so anything would help.

But, I think it's a bit unfair to make, what appears to be, a very bold assertion, without explaining it or allowing criticism. I have no interest (or qualification) to criticize your sources, but I would hope that someone would criticize mine.

I've only heard of evidence against, that interviews of US soldiers post WWII found only 1/4 had shot to kill. I've never really looked into it; the claim is somewhat disputed, I think.

The two commonly cited books: https://en.wikipedia.org/wiki/S.L.A._Marshall https://en.wikipedia.org/wiki/On_Killing

r/AskHistorians doubts it: https://redd.it/22o24j https://redd.it/2od6eg

Soldiers? Many wars are fought for unjust reasons, and soldiers just obey orders without considering if the orders are justified (e.g. Russians in Ukrainian, US in Irak, Dutch soldiers in Indonesia after WW2)

None of these are a "large fraction" of people.

edit: for an example, the entire US military is around 0.45% of the population. Only a small fraction of that is not purely support. Around 0.2% of the population are police. The vast majority never kill anyone.

Millions of soldiers is significant, even if it is low in percentages.

There are more people in the army then there are women having abortions, so if abortions is a big enough issue to address, people killing in the name of should also be considered an issue.