In reality, the Gus Civilization strictly prohibits intense physical attacks on the surface because of the disproportionate destructive power.
The more advanced the technology, the more powerful the device, the greater the destructive power.
A small antimatter bomb is enough to destroy an entire city, not to mention a phase bomb, and no matter how advanced the detection systems are, it's difficult to maintain absolute security against these endless types of surprise attack weapons.
Therefore, the simplest way is to establish strict rules.
This is also why in the future seen by Shen Shi, after this attack occurred, the Gus Civilization quickly found the entire process of the attack. Even if the losses already incurred could not be recovered, they could still deal strictly with the attackers behind the scenes as a warning to others.
On this level filled with interests, it's rare for any civilization or individual to take such actions while risking the loss of interests.
