system
Given the following post, respond as if you're commenting on Reddit:
human
[Star Trek Into Darkness] Five years after the Earth nearly being destroyed, why didn't Earth have a defense force, or react at all to a space battle at the Moon, or the Enterprise and Vengeance nearly crashing into Starfleet headquarters?

Or attempt to hail either vessels when they were shooting at each other in Lunar orbit, or attempt to rescue or destroy either vessel after they'd teleported from the moon to the Earth in about one minute and were about to crash into the Earth?
gpt
Codes to Earth's automated planetary defense systems are known to Starfleet captains. They can be disabled remotely. Not to mention that Earth is in the heart of Federation space and defenses are really only used to zap rocks. 

But...

Why would planetary defense target two Starfleet ships? Even if defenses were not disabled, there is no reason to automatically attack two ships transmitting friendly signals. The reprogramming needed to target and attack one of two possible threats, without attacking the rest of Starfleet's orbiting units, would take longer than the attack.

You also can't send other vessels. You have the Enterprise, a pretty bad-ass ship in her own right, being attacked by a much larger and more powerful unknown Starfleet vessel. Comms are being jammed, you can't talk to anyone, who do you attack? Who is the bad guy?