Thing, Stuff, and Items

What is the significance of the lack of initial hostility from the 'thing' towards the humans and their relative unabashed hostility towards it?

The movie opens with a scene of a man riding in a helicopter, hunting a seemingly harmless dog. He has a rifle and continues to shoot at him, missing on each shot. They get to a set of structures that seem to be a base of sorts and a group of American's emerge. They question the evident insanity in the man who is shooting at the dog, deciding to prevent an altercation that could lead to harm of one of there own. They shoot the man with the rifle and decide to take in the dog he was hunting. Up to this point, the dog has done nothing harmful or malicious towards anyone, instead it has simply been staying alive. The film continues and shows the dog(thing) harmlessly mingling with the humans inside in the base. A man starts to get angry at the individual who was 'looking out' for the dog and forces him to put him the animal with the rest. Before this though, there is a scene of the men eating food, specifically meat, and I feel this is important. The dog has scene the humans eating other beings of flesh and possibly has decided that it is morally acceptable to do this itself if its existence depends upon it. The thing gets put into the cage with the other dogs and starts to 'feed' upon one of them. This is no different morally than humans eating cows or whatever our meat of choice is, but this is where hostility towards the creature is reawakened.

What is the importance of the reawakened hostility towards the thing and how does this effect its actions that it follows afterward?

Put yourself into a situation where everyone is yelling at you, saying not to do the single thing you must do to survive. You will either die or do it. Primordial urges will force you to do it, unless you are a bonzo practicing monk that has more self-control than the average person. You do the thing, be it eating or breathing, and then the group around your attempts to kill you. Fear takes over and you will either fight or run away. Intelligence will most likely say to run when you are overwhelmed both physically and by number, so you try to run. Instead of getting away, you are followed by men spouting flame and explosives towards you but you just cannot understand why they are doing this. I feel that this is exactly what is happening in the movie. The 'thing' is being brutally hunted for doing nothing. Men are blatantly being dumb and not questioning the intentions of the 'thing'. They automatically assume that the thing that is different from them is malicious and relatively evil.