The Immortal Barbarian Star was the biggest competitor of the Norton Star as it was booming in its production of mechs. As humans were engaged in skirmishes with the Norton Star before conducting expeditions in Andromeda, this created historical resentment between Immortal Barbarian and Norton. Although this has faded over time, the rivalry between them has not as both wanted to be the main star in Andromeda.
Solon had a headache because this affair was caused by Skeleton, who had displayed his capabilities and taught the people on the Norton Star a lesson. This allowed the Immortal Barbarian players to find a target.
Abusing people on Earth would equate to a lesson for the people of the Norton star. Since you were abused by people on Earth and if we manage to return the favor to them, you people of Norton would have to fear us Immortal Barbarian people more in the future.