system
Given the following post, respond as if you're commenting on Reddit:
human
[Alien Covenant] SPOILERS

 Why did David decimate the Engineer's planet? 

Why didn't the engineers have some sort of docking  security procedure whereby they would communicate with their old ship that unexpectedly arrived home, confirming it's friendly intentions rather than blindly welcoming it with open arms? 

Did any engineers who were off planet when David deployed the pathogen respond? 

If the engineers were mad at us before, won't they be really mad now, and try to exterminate us post haste? 

How exactly did David become a genocidal psychopath?
gpt
He saw that they were no better than humans and that the Engineers would pose a hindrance to his isolated life on Paradise.

Not to mention that he may have some programmed bias on finding out more about xenobiology.

We're still not sure on the context of the whole thing with docking with David's ship. The Paradise Engineers seemed more primitive. Perhaps they saw that one of their own ships (after being missing for 2000 years) showed up. Perhaps the military base succeeded in annihilating those pesky humans? Better ask the Engineer pilots of that ship what went down. If they returned, they were certainly war heroes.

Whoops, looks like there's a... human? And he's watching the weapons load...? Oh noes, it all launched. RIP Engineers.