I think with these kinds of suits the core conceit is that gun manufacturing/sales is a sordid, immoral business along the lines of cigarettes, and that the very existence of a consumer market for their product implies their misuse and negative impact on society. Therefore, they should bear more responsibility for that impact.
They were emboldened by the suit against Bushmaster/Remington that succeeded and ultimately bankrupted Freedom Group.
The US being the bad guys in the Korean conflict is an interesting take that I wouldn't expect anyone outside of lemmygrad to espouse, care to elaborate?