I think Sawyer answered your question Oner, but just in case . . .
Basically, it's just that Thornton is placed in an environment full of hostiles. There's no ambiguity as to who he is or what he's doing, he just pretty much gets attacked whenever he gets spotted except with scripted dialogues. Contrast that with the hitman games, where your behavior tends to determine who is hostile towards you.
IMO, the latter offers a lot more playstyle flexibility and is very "spy," which is what bugged me most about finding out it didn't exist via this thread.