When someone is having major issues in their life that are totally unrelated to you but for some insane reason they are taking it out on you. You are now collateral damage in a fight that they should be having with someone else.
When Julie caught Tommy cheating on her she became convinced that all her friends were sleeping with him. She exploded on everyone and we were all collateral damage.
Coochie gained from roasting someone in the process of getting coochie. A vulturistic tactic of turning coochiful interest away from someone getting coochie to steal said coochie.
The boys roasted Martin when he was showing a girl falcon heavy landing clips in an attempt to have her become disinterested in Martin and obtain that Collateral Coochie.
When someone alters a Wikipedia article to win a specific argument, anyone who reads the false article before the "error" is corrected suffers from collateral misinformation.
I changed the scientific classification of red foxes last night in order to win an argument with Judy. I hope some stupid High School student didn't suffer from collateral misinformation.
Harry: Yo Dawg, I will let you borrow my broken watch, my cassette tape player and my last loaf of bread so I can get some rock!
Pusherman:damn you Collateral Fiend, gimme your bread and some stuff to make a sandwich and you got a deal!
Harry: sounds good, I'll be right back!