This is widely naïve for a variety of reasons, both conceptually and in practice.
Firstly you only need 1 person to pull the trigger, the rest just bring the people in or hold them down/tie them up first.
For a more historical look here's a brief follow up essay by Milgram after his famous experiments.
The perils of obedience
It's short but highly informative and goes into detail about specific subjects in the experiments.
For a more contempary example, consider all the people and even parents that forced masks on struggling and unwilling children over the last few years. How many Parents did that to their own children? What do you think they'd do to someone else's children?
And on a conceptual level, what makes you think these "good guys" in the police/military are going to stand up?
Lets take an example and use our very own Based Barbarian, Anticausal, no doubt he has an extensive file with numerous intelligence agencies. Lets say that someone decides he's a LiTeRaL NaZi and decides to arrange a swat team to arrest him in his home, since he lives in a deep red county all of his local Swat guys are "good guys"
The scenario will go something like this. Those good guys will leave their families in the morning and turn up to work and see AC's face with the dossier of his alleged crimes with the instructions "intelligence believes he is the ring leader of a white supremacist neo nazi group that is in the process of formenting armed revolt against the US, serve this arrest warrant at this address today"
At what point will they stand up and refuse to follow those orders?
Is it when they take the intelligence home and review it for themselves over the next few weeks?
Is it when they raid his house and see his extensive library and lack of anything criminal and decide to take the cuffs off and go home? Or will it be when he points out that he is innocent and that they are acting as jack booted stormtroopers following orders?
Help me out here, at what point do you envisage the "good guys" making the call to stand up and make a stand?
The banality of evil is just that, banal. It's just going to be some bored and overworked dude acting as a cog in the machine unwittingly committing a small enough part of evil that they don't notice.