No, I am sorry.... its not "OBVIOUS" to me. Nowhere is this made clear in the film.
Oh, it was made pretty clear...did you even watch the movie? Two thousand year old corpses. When Shaw asks David about why the ship was headed to Earth two thousand years ago before they wake the Engineer, he even says "To create, one must first destroy" or somthing to that effect. If you didn't get this, you weren't paying any attention.
If they were supposed to destroy us, why would they waste time on an outpost light-years away from Earth? its not like they DIDNT KNOW WHERE EARTH WAS, and its not an efficient use of time.
I'm sorry..what are you talking about? You're not making any sense. The outpost was a military base (or so Janek believes), and they were most likely preparing to take their bioweapon cargo from their bioweapon factory to Earth before somthing went wrong..and they were (almost) all killed. Which was also clearly understood if you paid attention during the film.
The awakened Engineer has been asleep for thousands of years. Then all the sudden he's patting David on the head, until David makes his request. His hulking out had nothing to do with a predetermined mission, and everything to do with David's message ticking him off for some reason.
That reason is unknown to the audience.
Now you're acting as if your opinion is a complete fact.
David speaks to the Engineer BEFORE he pats him on the head. Pay attention.
So, no, you can't say with complete certainty that whatever David said is what caused him to kill the crew. We can speculate that he was most likely going to kill them either way. He doesn't give a ____ about our silly problems (weyland wanting to live forever). He took a few seconds to analyze the situation and make a decision.
He knew what needed to be done. He knew that whatever threat that killed his crew mates two thousand years ago must have been long gone if the humans made it there alive. He knew that humans had evolved a great deal. He knew that he needed to complete his mission ASAP.
..and he probably stroked David's hair because he found him to be interesting or pure because he was actually capable of speaking the Engineer language. Or because he was slightly amazed at how far one of his race's own creations have come....they were now able to create life themselves.
It really seems like you just had no idea what was going on in the movie because you didn't pay attention, or didn't want to in the first place.
Look, you love Prometheus. We get that. But your rationales ring hollow to those of us who have probably been following this franchise since before you were born.
Once again you bring the age thing into play. Fifth time.
Doesn't that make you look even worse considering the fact that you are older and apparently far superior to me, yet you had almost no idea of what was happening in the movie that you've "been following since before I was born"?