I mentioned the game's difficulty earlier, and this, too, is important for its message. The act of killing is, itself, a minor failure, no matter how justified it is. And even if that is the case, killing a suspect prevents you from getting full marks on a mission.
Even after you issue that warning, you do not get a "clean kill" unless the suspect is aiming at a police officer or a civilian. You must give the suspect fair warning and a chance to surrender (specifically, by shouting "Police! Drop your weapon!"). To that end, there are rules that you must abide by. It is your first priority to arrest suspects, not to kill them. In SWAT 4 - which is more serious than LCS by far - you are playing a police officer. Even though the game is intentionally designed to be over-the-top political satire, the characters in that game behave more "humanly" than most other characters do. Characters have a sense of self-preservation, cowardice, or moral ambiguity.
You can use realistic options to manipulate the situation in your favor, and people will behave in a relatively realistic manner. In LCS, every combat encounter has more options than just "shooting". It is a thing almost every other shooter ever made fails at. This is a thing that LCS and SWAT 4 acknowledge. People don't behave the same they make their own decisions based on their own adrenaline-fueled emotional state. Some people are dedicated enough to keep fighting even when they're certain they're going to die. In real life, people have a variety of reactions to a combat situation. LCS and SWAT 4 have one important thing in common, though, and it's what separates SWAT 4 from Rainbow Six et al: the way characters, especially hostile characters, behave. LCS' methods range from "subversive" to "terrorist", SWAT 4 is about going by-the-book at all times. LCS is about creating social change, SWAT 4 is about preserving order.
I wrote a while back about Liberal Crime Squad, a game that in many ways is on the opposite side of SWAT 4. But there's a big difference between SWAT 4 and those other games as well.
The gameplay is tense and things can go bad in a few short seconds. People go down in one or two shots, making tactics and fast reflexes a necessity. In many ways it is easy to compare SWAT 4 to other "realistic" shooters like ARMA or Rainbow 6. The player takes the role of a police SWAT team leader and is tasked with "restoring order to chaos" in a variety of scenarios ranging from robbery to terrorism. SWAT 4 is a first-person, squad-based tactical shooter. EDIT: When this article was written, SWAT 4 was not on any digital services and was difficult to obtain.