Answer:
fear or dislike of countries that aren`t your own
Spartacues would have lead a mass revolt and lead the empire to impload and form small states
William Pitt the Younger was a Prime Minister from England. The Reign of Terror happened in France. They were not related to each other's country.
The Persians were much less democratic and usually had local rulers that ruled with an iron fist while working for the main emperor. Had he beaten Alexander, chances are that he wouldn't allow religious and cultural freedoms in Alexander's territory the same way that Alexander allowed in conquered Persian territories.