Do Republic loyalist Parties receive Corruption if they attack a Party in rebellion?
Only if they decide to keep the Sector. From the Republic’s perspective, the Rebellion is treated much like an Infestation. So ‘liberating’ an Infested or Rebellion Sector and making it free and neutral (ie. not possessed by any Party) is perfectly fine. This is one of the main things that the Republic Fleet exists for. However, if a Party attacks a Sector that the Rebellion controls, and takes it for themselves, then it is a corrupt act and the Invading Party gains the 2 Corruption tokens. Remember to declare that you’re Invading and taking the Sector during your Fleet movements. So making Sectors neutral gains no Corruption. Taking them for yourself does.