Doesnt make sense

If the blue men are indeed the creators of life throught the universe such as earth or whatever. If they are Gods or whatever. Or if the species that created the creators and left them in charge. WHY in Gods name would they want to go back to earth to destroy everything they created? Why create the Alien which we all know is a killing machine without remorse or sentient thinking? If blue man isnt one of the original species of creators how the hell does he know how to fly the ship and use its technology? Im pretty sure that the guy with the ginger mohawk and tatoos is our blue man.....or if not hes infected with something cos its him lunging at another crew member then throws the crew member in the vehicle bay on Prometheus.....you can tell from the hair. That ship is on THAT planet for a reason other than creating life then destroying it again when they found out that man didnt turn out the way that was intended. Why would they interfere with natural evolution in the first place? Most of the logical human race thinks we are here from natural evolution.....what would be the purpose of otherwise to a race of more advanced beings? To what end? What do they think they would achieve? If they are so advanced they would also know that you cant attain perfection, not through lack of trying. But because, as Dr Ian Malcom said "Life finds a way" So any race human or otherwise, no matter how sophisticated cannot alter nature or the order of the universe and if our alien species whoever they are disregard this knowledge then they cant be that advanced can they? So why create a race then want to kill it......its like killing your children. They knew when they left the cave paintings etc that we were becoming advanced from when they (if they did) seeded the earth.....which i highly doubt. They knew then that we could become more civilised and capable of space travel.....else why leave the paintings? You dont leave a map to people that cant read a map do you? Then and heres the big one.......If they hoped that we became so technoligical to the point that we could follow their directions......why do they turn out to be so hostile. Wouldnt they welcome us with open arms?