In your example with Sam and Bob, I see two people who are in different groups and can have identical (or highly coherent) belief systems.
If you want to split Sam and Bob up so that they won't be friends any more and they will hate each other, you do that by twisting their beliefs.
First one might suggest that members of Sam's faith, while in the military, were kept from the riskest parts of combat because the military. Then you convince Bob that anyone who plays football is just asking for CTE and that any friend you have is going to turn into a raging monster one of these days, and then you convince Sam, that Bob and others in his religous sect are perverting American politics to keep people like Sam from achieving similar level of success. And you convince Bob that it is Sam "and people like him" who are responsible for the cost of getting a new car or the reason jobs have left the area.
The next thing you know, Sam and Bob hate each other.
My point is that this can be done by carefully setting up what Sam and Bob believe, regardless of what groups they belong to. There are examples all around us today of families that have gone from groups of like minded people to separate camps, lifelong friends that one can no longer talk to.
This is Propaganda, this is Brain Washing, this is the corruption of a group through alternative belief systems.
And its the topic at hand, "Surviving Jonestown".
Because it’s really not about people it’s about aspects of people.
Let’s say Sam is a Packers fan. Now Bob is a member of the Packers football team so on Sunday their part of the same in group.
But, on Election Day Sam is a Dem and Bob a Republican so the must fight.
But their both Americans who are part of the army reserve, so they are brothers in arms willing to risk their lives for each other.
But, they are part of different faiths, and ...
So, this vilification is about context. The football team you need to beat today, may need to beat some other team next week to get you into the playoffs etc etc.